Syntax highlight the JavaScript keyword using.

The ECMAScript Explicit Resource Management proposal (stage 3) that specifies the  keyword `using`:

https://github.com/tc39/proposal-explicit-resource-management

This has already been done for the TypeScript and TSX languages:

- #14762
- #14772

crates/languages/src/javascript/highlights.scm

@@ -194,6 +194,7 @@
   "throw"
   "try"
   "typeof"
+  "using"
   "var"
   "void"
   "while"