lang(json): make field key highlighting consistent with toml and yaml (#10676)

runtime/queries/json/highlights.scm

@@ -4,8 +4,9 @@
 ] @constant.builtin.boolean
 (null) @constant.builtin
 (number) @constant.numeric
+
 (pair
-  key: (_) @keyword)
+  key: (_) @variable.other.member)
 
 (string) @string
 (escape_sequence) @constant.character.escape

runtime/queries/json5/highlights.scm

@@ -1,11 +1,20 @@
-(string) @string
-
-(identifier) @constant
-
-(number) @constant.numeric
-
+[
+  (true)
+  (false)
+] @constant.builtin.boolean
 (null) @constant.builtin
+(number) @constant.numeric
 
-[(true) (false)] @constant.builtin.boolean
+(member
+  name: (_) @variable.other.member)
 
+(string) @string
 (comment) @comment
+
+"," @punctuation.delimiter
+[
+  "["
+  "]"
+  "{"
+  "}"
+] @punctuation.bracket