Adding union to be recognized as a keyword in Rust

[Jaebaek-Lee]

Adding union to be recognized as a keyword in Rust.

#3948

Changes

Added the union keyword to the KEYWORDS array in rust.js.

Checklist

• Added markup tests, or they don't apply here because...
  Even without adding any markup tests, the following code ensures that the highlighting is applied correctly.

        begin: [
          /(?:trait|enum|struct|union|impl|for)/,
          /\s+/,
          UNDERSCORE_IDENT_RE
        ],
        className: {
          1: "keyword",
          3: "title.class"
        }

• Updated the changelog at CHANGES.md

[github-actions]

Build Size Report

Changes to minified artifacts in /build, after gzip compression.

3 files changed

Total change +4 B

View Changes

file	base	pr	diff
es/languages/rust.min.js	1.48 KB	1.49 KB	+3 B
highlight.min.js	8.21 KB	8.21 KB	-1 B
languages/rust.min.js	1.49 KB	1.49 KB	+2 B

[joshgoebel]

Please also provide a test case of union used in context (outside of defining a union)... see tests/markup, etc.

[Jaebaek-Lee]

As I commented in the issue #3948, union is not commonly used except when defining unions, so I didn't write a separate test case for it.
Of course, It can be used outside of defining a union, such as let r#union, but that's not relevant to this issue, as it's a case of the regex not recognizing union as a keyword.

[joshgoebel]

union is not commonly used except when defining unions, so I didn't write a separate test case for it.

Can you provide at least one sample usage outside of a union declaration other than r#union? The keywords list is not necessarily intended to be exhaustive if the keywords already have their own separate rules.

[github-actions]

Build Size Report

Changes to minified artifacts in /build, after gzip compression.

2 files changed

Total change +5 B

View Changes

file	base	pr	diff
es/languages/rust.min.js	1.48 KB	1.49 KB	+3 B
languages/rust.min.js	1.49 KB	1.49 KB	+2 B