Defining quoted enum values should be supported

Description of problem

Given an enum with, say, the enum-value of "standard", it would be nice to support:

<pre class="idl">
enum Foo {
   "standard"
};
</pre>
<dfn>"standard"</dfn>

What happened (e.g., it crashed)?:

That's not supported (or doesn't work).

Expected behavior (e.g., it shouldn't crash):

It should be possible to support that, if the context is an enum.

Note that <dfn>""</dfn> is supported, so it follows that <dfn>"whatever"</dfn> should be supported too.

Locate the enum parsing and quoted-value handling in the JavaScript source, then inspect how the existing empty-string case is supported. Confirm the quoted enum example from the issue is accepted without affecting non-enum definitions, and add or update the relevant tests if the project has coverage for this parser behavior.