Add other commands

Author: QazCetelic

book/nushell_map_functional.md

@@ -8,29 +8,29 @@ Note: this table assumes Nu 0.43 or later.
 |------------------------------------------------|------------------------------|---------------------------------|--------------------------|
 | [append](../commands/docs/append.md)           | conj, into, concat           | append, (++), concat, concatMap | (++)                     |
 | [into binary](../commands/docs/into_binary.md) | Integer/toHexString          |                                 | showHex                  |
-| count                                          | count                        | length, size                    | length, size             |
+| [length](../commands/docs/length.md)           | count                        | length, size                    | length, size             |
 | [date](../commands/docs/date.md)               | java.time.LocalDate/now      |                                 |                          |
 | [each](../commands/docs/each.md)               | map, mapv, iterate           | map, forEach                    | map, mapM                |
 | [exit](../commands/docs/each.md)               | System/exit                  |                                 |                          |
 | [first](../commands/docs/first.md)             | first                        | head                            | head                     |
 | [format](../commands/docs/format.md)           | format                       |                                 | Text.Printf.printf       |
 | [group-by](../commands/docs/group-by.md)       | group-by                     |                                 | group, groupBy           |
-| help                                           | doc                          |                                 |                          |
+| [help](../cookbook/help.md)                    | doc                          |                                 |                          |
 | [is-empty](../commands/docs/is-empty.md)       | empty?                       | isEmpty                         |                          |
 | [last](../commands/docs/last.md)               | last, peek, take-last        | last                            | last                     |
 | [lines](../commands/docs/lines.md)             |                              |                                 | lines, words, split-with |
 | [match](../commands/docs/match.md)             |                              | match (Ocaml), case (Elm)       | case                     |
-| nth                                            | nth                          | Array.get                       | lookup                   |
+| [select](../commands/docs/select.md)           | nth                          | Array.get                       | lookup                   |
 | [open](../commands/docs/open.md)               | with-open                    |                                 |                          |
 | [transpose](../commands/docs/transpose.md)     | (apply mapv vector matrix)   |                                 | transpose                |
 | [prepend](../commands/docs/prepend.md)         | cons                         | cons, ::                        | ::                       |
 | [print](../commands/docs/print.md)             | println                      |                                 | putStrLn, print          |
-| range, 1..10                                   | range                        | range                           | 1..10, 'a'..'f'          |
+| [slice](../commands/docs/slice.md), 1..10      | range                        | range                           | 1..10, 'a'..'f'          |
 | [reduce](../commands/docs/reduce.md)           | reduce, reduce-kv            | foldr                           | foldr                    |
 | [reverse](../commands/docs/reverse.md)         | reverse, rseq                | reverse, reverseInPlace         | reverse                  |
 | [select](../commands/docs/select.md)           | select-keys                  |                                 |                          |
 | [shuffle](../commands/docs/shuffle.md)         | shuffle                      |                                 |                          |
-| size                                           | count                        |                                 | size, length             |
+| [length](../commands/docs/length.md)           | count                        |                                 | size, length             |
 | [skip](../commands/docs/skip.md)               | rest                         | tail                            | tail                     |
 | [skip until](../commands/docs/skip_until.md)   | drop-while                   |                                 |                          |
 | [skip while](../commands/docs/skip_while.md)   | drop-while                   | dropWhile                       | dropWhile, dropWhileEnd  |
@@ -39,10 +39,9 @@ Note: this table assumes Nu 0.43 or later.
 | [str](../commands/docs/str.md)                 | clojure.string functions     | String functions                |                          |
 | [str join](../commands/docs/str_join.md)       | join                         | concat                          | intercalate              |
 | [str trim](../commands/docs/str_trim.md)       | trim, triml, trimr           | trim, trimLeft, trimRight       | strip                    |
-| sum                                            | apply +                      | sum                             | sum                      |
+| [math sum](../commands/docs/math_sum.md)       | apply +                      | sum                             | sum                      |
 | [take](../commands/docs/take.md)               | take, drop-last, pop         | take, init                      | take, init               |
 | [take until](../commands/docs/take_until.md)   | take-while                   | takeWhile                       | takeWhile                |
 | [take while](../commands/docs/take_while.md)   | take-while                   | takeWhile                       | takeWhile                |
 | [uniq](../commands/docs/uniq.md)               | set                          | Set.empty                       | Data.Set                 |
 | [where](../commands/docs/where.md)             | filter, filterv, select      | filter, filterMap               | filter                   |
-