fix(queries): register highlights and remove invalid node capture

queries/highlights.scm

@@ -0,0 +1,8 @@
+(keyword) @keyword
+
+(key) @property
+(assert_key) @property
+
+(quoted_value) @string
+(template_value) @variable.special
+(bare_value) @string.unquoted

tree-sitter.json

@@ -6,6 +6,7 @@
       "camelcase": "Bruno",
       "title": "Bruno",
       "scope": "source.bruno",
+      "highlights": "queries/highlights.scm",
       "file-types": [
         "bru"
       ],
@@ -37,4 +38,3 @@
     "zig": false
   }
 }
-