Adds LWC Parser to support unquoted interop attributes (#5800)

This pull requests adds a new parser option `lwc`. This is the same as the HTML parser, but it adds support for unquoted HTML attributes per the needs of LWC. See: #5627

website/playground/codeSamples.js

@@ -285,6 +285,7 @@ export default function(parser) {
       ].join("\n");
     case "html":
     case "angular":
+    case "lwc":
       return [
         "<!DOCTYPE html>",
         '<HTML CLASS="no-js mY-ClAsS">',