Fix tree-sitter highlighting

tree-sitter-kerolox/queries/highlights.scm

@@ -1,14 +1,17 @@
 ; TODO: automate highlighting testing
+; TODO: ensure that name segments are highlighted correctly in each context
 
 (comment) @comment.line
 (integer) @constant.numeric
+(string) @string.quoted
+(escape_sequence) @constant.character.escape
 (variable) @variable
-(expr (symbol) @constant)
+(expr symbol: _ @constant)
 (import (symbol) @module)
-(type (symbol)) @type
+(type (name)) @type
 (type_alias name: _ @type)
 
-(rule relation: (symbol) @constructor)
+(rule relation: (name) @constructor)
 (relation name: (symbol) @function)
 (apply head: _ @function)