Update README.md

Add description for syntax when setting multiple [k, v] pairs on conflict

Author: Anton Oellerer

README.md

@@ -92,6 +92,15 @@ The query creation and usage is exactly the same as honeysql.
     sql/format)
 => ["INSERT INTO distributors (did, dname) VALUES (23, ?) ON CONFLICT (did) DO UPDATE SET dname = ?" "Foo Distributors" "EXCLUDED.dname || ' (formerly ' || d.dname || ')'"]
 ```
+To set multiple fields on conflict, add the `[k, v]` statements like this:
+```clj
+(-> (insert-into :distributors)
+    (values [{:did 23 :dname "Foo Distributors"}])
+    (psqlh/on-conflict :did)
+    (psqlh/do-update-set! [:dname "EXCLUDED.dname || ' (formerly ' || distributors.dname || ')'"] [:downer "EXCLUDED.downer"])
+    sql/format)
+=> ["INSERT INTO distributors (did, dname) VALUES (23, ?) ON CONFLICT (did) DO UPDATE SET dname = ?, downer = ?" "Foo Distributors" "EXCLUDED.dname || ' (formerly ' || d.dname || ')'" "EXCLUDED.downer"]
+```
 
 ### insert into with alias
 `insert-into-as` can be used to write insert statements with table name aliased.