Use textContent to avoid HTML special characters in options

[ggorlen]

Resolves #5778

Changes:

• Use textContent rather than innerHTML to set and compare options in a select menu, avoiding parsing HTML and escaping HTML special characters that might happen to be in the string (see linked issue for details).
• Add unit test with HTML special characters that fails on the old innerHTML and passes on textContent.

PR Checklist

• npm run lint passes
• Inline documentation is included / updated
• Unit tests are included / updated

[limzykenneth]

Looks good. Thanks!

@all-contributors please add @ggorlen for code

[allcontributors]

@limzykenneth

I've put up a pull request to add @ggorlen! 🎉