[minor] Fix typos

Author: Wilfred

crates/hir-def/src/lib.rs

@@ -1245,7 +1245,7 @@ pub struct SyntheticSyntax;
 // Crate authors can opt their type out of completions in some cases.
 // This is done with the `#[rust_analyzer::completions(...)]` attribute.
 //
-// All completeable things support `#[rust_analyzer::completions(ignore_flyimport)]`,
+// All completable things support `#[rust_analyzer::completions(ignore_flyimport)]`,
 // which causes the thing to get excluded from flyimport completion. It will still
 // be completed when in scope. This is analogous to the setting `rust-analyzer.completion.autoimport.exclude`
 // with `"type": "always"`.

docs/book/README.md

@@ -19,7 +19,7 @@ mdbook will rebuild the documentation as changes are made.
 
 ## Making updates
 
-While not required, installing the mdbook binary can be helfpul in order to see the changes.
+While not required, installing the mdbook binary can be helpful in order to see the changes.
 Start with the mdbook [User Guide](https://rust-lang.github.io/mdBook/guide/installation.html) to familiarize yourself with the tool.
 
 ## Generated documentation