Highlight identifier after 'impl' keyword in Rust language definition

Hi! 👋

Firstly, thanks for your work on this project! 🙂

Today I used patch-package to patch highlight.js@9.18.3 for the project I’m working on.

It looks as if the identifier after the impl keyword is not being highlighted. I’ve added an extra element to the class definition to include impl.

Here is the diff that solved my problem:

diff --git a/node_modules/highlight.js/lib/languages/rust.js b/node_modules/highlight.js/lib/languages/rust.js
index 5e2af44..590dc15 100644
--- a/node_modules/highlight.js/lib/languages/rust.js
+++ b/node_modules/highlight.js/lib/languages/rust.js
@@ -89,7 +89,7 @@ module.exports = function(hljs) {
       },
       {
         className: 'class',
-        beginKeywords: 'trait enum struct union', end: '{',
+        beginKeywords: 'trait enum struct union impl', end: '{',
         contains: [
           hljs.inherit(hljs.UNDERSCORE_TITLE_MODE, {endsParent: true})
         ],

This issue body was partially generated by patch-package.

[RunDevelopment]

Isn’t for just a keyword in all cases?

Yes, it is. Sorry for being clear here. I meant that it would strange that in impl Trait for Foo {} only Trait would be highlighted as a class name even though Foo obviously is one as well.

[joshgoebel]

I’ve made a lot of other changes a cleanups in the simpler struct PR: https://github.com/highlightjs/highlight.js/pull/3078/commits/9d6befcd93ac334b62502c86efb5214f8eaa1eac