highlights(zig): highlight enum,union,error and custom number type

* highlight enum field as a constant
 * highlight cImport and constructor
 * highlight else_switch

enum constant

queries/zig/highlights.scm

@@ -27,13 +27,19 @@
 
 (build_in_call_expr
   function: ((identifier) @include
-             (#eq? @include "@import"))
+             (#any-of? @include "@import" "@cImport"))
+)
+(struct_construction
+  (type_identifier) @constructor
 )
-
 ;; other identifiers
 (type_identifier) @type
+(custom_number_type) @type.builtin
 (primitive_type) @type.builtin
 (field_identifier) @field
+(enum_identifier) @constant
+(union_identifier) @field
+(error_identifier) @field
 
 (line_comment) @comment
 (doc_comment) @comment
@@ -121,6 +127,7 @@
 "fn" @keyword.function
 
 [
+  (else_switch)
   "continue"
   "else"
   "if"