Allow to skip testing for URLs

[fulldecent]

Automated testing for twitter.com always fails.

Let's find a way to skip this an other URLs as needed:

Work plan

• [x] Add file tests/skip-urls.regex.txt
  • [x] Add https://dont-check-this.example.com
  • [x] Add https://.*.twitter.com/.*
• [x] Load and use this file from plugin.html-validate.external-links.mjs
• [x] Add a test fixture with link to https://dont-check-this.example.com and ensure it is not fetched

[fulldecent]

Please add a new test so you can see if this feature is actually working

[Raza403]

OK, I added this one in external links test.

[fulldecent]

Good ready to deploy this to all sites now

[fulldecent]

This is deployed