highlights(bash): rework keywords section

* Use more specified scope when possible for keywords like @keyword.repeat.
* Add more keywords like "local" or "unsetenv".

Limitation:
* Bash doesn't allow you to have a local variable outside of a function, so maybe we need to have better queries to not highlight the local in this case.
* If we name a function with a keyword (such as unset or local), it will use the highlight scope "keyword" instead of "function".

runtime/queries/bash/highlights.scm

@@ -10,23 +10,37 @@
 (variable_name) @variable.other.member
 
 [
+  "if"
+  "then"
+  "else"
+  "elif"
+  "fi"
   "case"
+  "in"
+  "esac"
+] @keyword.control.conditional
+
+[
+  "for"
   "do"
   "done"
-  "elif"
-  "else"
-  "esac"
+  "select"
+  "until"
+  "while"
+] @keyword.control.repeat
+
+[
+  "declare"
+  "typeset"
   "export"
-  "fi"
-  "for"
-  "function"
-  "if"
-  "in"
+  "readonly"
+  "local"
   "unset"
-  "while"
-  "then"
+  "unsetenv"
 ] @keyword
 
+"function" @keyword.function
+
 (comment) @comment
 
 (function_definition name: (word) @function)