nvim queries: Conform to commonly used highlight names (#99)

This updates:

| Query | Highlight name | Like in... |
|-|-|-|
| Punctuation `:`, `,` | `punctuation.special` | TOML, Bash, JSON, ... |
| Key fields in tables/records | `variable.member` | Go, Zig, V, TOML |
| Returns `->` | `punctuation.special` | Rust |
| Variable `$` | `punctuation.special` | Bash, Awk |
| Variable identifier | `variable` | Bash, Awk, Perl, Fish |
| Shebang | `keyword.directive` | Bash, Awk |
| Built-in types | `type` | Zig et al[^1] |
| Numbers | `number` | Zig, Rust, Python, TOML, Bash, ... |
| Arguments | `variable.parameter` |  Bash[^2] |
| Redirect operator | `operator` | Bash, Fish |
| Redirect destination | `variable.parameter` | Bash |

[^1]: Note that for built-in types, languages like Rust, Python, Go
differentiates highlights of built-in types and other types (such as
structs), but there are no other types in Nu, I'll leave this up to
debate, IMO a generic type will suffice here.

[^2]: Perl, Fish and Awk all leave these unhighlighted.

Also adds highlights for documentation comments for functions and
parameters.

I've tried to put newly introduced highlight queries into the correct
groups in the file, let me know if there are any other prevailing styles
I should follow!

queries/nu/highlights.scm

@@ -56,26 +56,28 @@
 
 ;;; ---
 ;;; literals
-(val_number) @constant.numeric
+(val_number) @number
 (val_duration unit: _ @variable.parameter)
 (val_filesize unit: _ @variable.parameter)
 (val_binary
  [
  "0b"
  "0o"
  "0x"
- ] @constant.numeric
+ ] @number
  "[" @punctuation.bracket
  digit: [
  "," @punctuation.delimiter
- (hex_digit) @constant.number
+ (hex_digit) @number
  ]
  "]" @punctuation.bracket
-) @constant.numeric
+) @number
 (val_bool) @constant.builtin
 (val_nothing) @constant.builtin
 (val_string) @string
-(val_date) @constant.number
+arg_str: (val_string) @variable.parameter
+file_path: (val_string) @variable.parameter
+(val_date) @number
 (inter_escape_sequence) @constant.character.escape
 (escape_sequence) @constant.character.escape
 (val_interpolated [
@@ -176,14 +178,14 @@
  "e>" "err>"
  "e+o>" "err+out>"
  "o+e>" "out+err>"
-] @special
+] @operator
 
 ;;; ---
 ;;; punctuation
 [
  ","
  ";"
-] @punctuation.delimiter
+] @punctuation.special
 
 (param_short_flag "-" @punctuation.delimiter)
 (param_long_flag ["--"] @punctuation.delimiter)
@@ -193,6 +195,7 @@
 (param_value ["="] @punctuation.special)
 (param_cmd ["@"] @punctuation.special)
 (param_opt ["?"] @punctuation.special)
+(returns "->" @punctuation.special)
 
 [
  "(" ")"
@@ -202,6 +205,8 @@
 
 (val_record
  (record_entry ":" @punctuation.delimiter))
+key: (identifier) @property
+
 ;;; ---
 ;;; identifiers
 (param_rest
@@ -234,17 +239,21 @@
 ) @variable.parameter
 
 (val_variable
- "$" @variable.parameter
+ "$" @punctuation.special
  [
- (identifier) @namespace
- "in"
- "nu"
- "env"
- ] @special
-)
+ (identifier) @variable
+ "in" @special
+ "nu" @namespace
+ "env" @constant
+ ]
+) @none
+
+(record_entry
+ ":" @punctuation.special)
+
 ;;; ---
 ;;; types
-(flat_type) @type.builtin
+(flat_type) @type
 (list_type
  "list" @type.enum
  ["<" ">"] @punctuation.bracket
@@ -253,9 +262,17 @@
  ["record" "table"] @type.enum
  "<" @punctuation.bracket
  key: (_) @variable.parameter
- ["," ":"] @punctuation.delimiter
+ ["," ":"] @punctuation.special
  ">" @punctuation.bracket
 )
 
-(shebang) @comment
+(shebang) @keyword.directive
 (comment) @comment
+(
+ (comment) @comment.documentation
+ (decl_def)
+)
+(
+ (parameter)
+ (comment) @comment.documentation
+)