feat!: align standard captures with upstream

Problem: Sharing highlight queries with upstream tree-sitter and
Helix is difficult.

Solution: Where reasonable, use capture names in tree-sitter's standard
list or Helix's Atom-style hierarchy.

Specifically:

* tree-sitter "standard capture names"
  (3f44b89685/highlight/src/lib.rs (L20-L72)):

  - `@parameter` -> `@variable.parameter`
  - `@field` -> `@variable.member`
  - `@namespace` -> `@module`
  - `@float` -> `@number.float`
  - `@symbol` -> `@string.special.symbol`
  - `@string.regex` -> `@string.regexp`
  - `@text.*` -> `@markup.*` (`strong`, `italic`, `link`, `strikethrough`; with exceptions; see below)
  - `@text.title` -> `@markup.heading`
  - `@text.literal` -> `@markup.raw`
  - `@text.reference` -> `@markup.link`
  - `@text.uri` -> `@markup.link.url` (in markup links)
  - `@string.special` -> `@markup.link.label` (non-url links)
  - `@punctuation.special` -> `@markup.list` (markdown lists only; move subitems from `@text.todo`)

* Helix captures
  (https://docs.helix-editor.com/master/themes.html#syntax-highlighting):

  - `@method` -> `@function.method`
  - `@method.call` -> `@function.method.call`
  - `@text.{todo,warning,note,danger}` -> `@comment.{error,warning,hint,info,todo}`
  - `@text.diff.{add,delete,}` -> `@diff.{plus,minus,delta}`
  - `@text.uri` -> `@string.special.url` (outside markup)
  - `@preproc` -> `@keyword.directive`
  - `@define` -> `@keyword.directive`(`.define`?)
  - `@storageclass` -> `@keyword.storage`
  - `@conditional` -> `@keyword.conditional`
  - `@debug` -> `@keyword.debug`
  - `@exception` -> `@keyword.exception`
  - `@include` -> `@keyword.import`
  - `@repeat` -> `@keyword.repeat`

* cleanup

  - remove some redundant `@conceal` (but still allow it for conceal-only patterns)
  - remove obsolete `@error` (syntax linting is out of scope for this repo)
  - sort, cleanup capture list in `CONTRIBUTING.md`

queries/luau/highlights.scm

@@ -1,6 +1,6 @@
 ; Preproc
 
-(hash_bang_line) @preproc
+(hash_bang_line) @keyword.directive
 
 ;; Keywords
 
@@ -23,18 +23,18 @@
   "while"
   "do"
   "end"
-] @repeat)
+] @keyword.repeat)
 
 (repeat_statement
 [
   "repeat"
   "until"
-] @repeat)
+] @keyword.repeat)
 
 [
   (break_statement)
   (continue_statement)
-] @repeat
+] @keyword.repeat
 
 (if_statement
 [
@@ -43,27 +43,27 @@
   "else"
   "then"
   "end"
-] @conditional)
+] @keyword.conditional)
 
 (elseif_statement
 [
   "elseif"
   "then"
   "end"
-] @conditional)
+] @keyword.conditional)
 
 (else_statement
 [
   "else"
   "end"
-] @conditional)
+] @keyword.conditional)
 
 (for_statement
 [
   "for"
   "do"
   "end"
-] @repeat)
+] @keyword.repeat)
 
 (function_declaration
 [
@@ -149,19 +149,19 @@
 ((identifier) @variable.builtin
   (#eq? @variable.builtin "self"))
 
-((identifier) @namespace.builtin
-  (#any-of? @namespace.builtin "_G" "debug" "io" "jit" "math" "os" "package" "string" "table" "utf8"))
+((identifier) @module.builtin
+  (#any-of? @module.builtin "_G" "debug" "io" "jit" "math" "os" "package" "string" "table" "utf8"))
 
 ((identifier) @keyword.coroutine
   (#eq? @keyword.coroutine "coroutine"))
 
 ;; Tables
 
-(field name: (identifier) @field)
+(field name: (identifier) @variable.member)
 
-(dot_index_expression field: (identifier) @field)
+(dot_index_expression field: (identifier) @variable.member)
 
-(object_type (identifier) @field)
+(object_type (identifier) @variable.member)
 
 (table_constructor
 [
@@ -171,8 +171,8 @@
 
 ; Functions
 
-(parameter . (identifier) @parameter)
-(function_type (identifier) @parameter)
+(parameter . (identifier) @variable.parameter)
+(function_type (identifier) @variable.parameter)
 
 (function_call name: (identifier) @function.call)
 (function_declaration name: (identifier) @function)
@@ -180,7 +180,7 @@
 (function_call name: (dot_index_expression field: (identifier) @function.call))
 (function_declaration name: (dot_index_expression field: (identifier) @function))
 
-(method_index_expression method: (identifier) @method.call)
+(method_index_expression method: (identifier) @function.method.call)
 
 (function_call
   (identifier) @function.builtin
@@ -252,11 +252,11 @@
   (dot_index_expression
     field: (identifier) @_method
     (#any-of? @_method "find" "format" "match" "gmatch" "gsub"))
-  arguments: (arguments . (_) . (string content: _ @string.regex)))
+  arguments: (arguments . (_) . (string content: _ @string.regexp)))
 
 ; ("123"):match("%d+")
 (function_call
   (method_index_expression
     method: (identifier) @_method
     (#any-of? @_method "find" "format" "match" "gmatch" "gsub"))
-    arguments: (arguments . (string content: _ @string.regex)))
+    arguments: (arguments . (string content: _ @string.regexp)))