Add select binding

grammar.js

@@ -164,9 +164,16 @@ module.exports = grammar({
       $._string_literal,
       $.boolean_literal,
       alias("any", $.any),
+      $.pattern_binding,
       alias("default", $.default),
     ),
 
+    pattern_binding: ($) => seq(
+      field("value", alias("any", $.any)),
+      field("operator", alias("@", $.operator)),
+      field("binding", $.identifier),
+    ),
+
     _case_value: ($) => choice(
       alias("unset", $.unset),
       $._expr,