fix external link filter

[KaiWaldrant]

Describe your changes

Remove "www." from publish link in link-external-filter. The published URL does not start with "www". This introduced a bug that on the published website internal links were recognised as an external URL.

Issue ticket number and link

Closes #202

Checklist before requesting a review

• [x] I have performed a self-review of my code

• Check the correct box. Does this PR contain:

  • [ ] Breaking changes
  • [ ] New functionality
  • [ ] Major changes
  • [ ] Minor changes
  • [x] Bug fixes

• [x] Proposed changes are described in the CHANGELOG.md

• [x] CI Preview succeeds and looks good!

[github-actions[bot]]

[KaiWaldrant]

We won't know if it fixes the issue unless we publish.