Inform users that Block Web fonts may break some elements on the page

[SimonBasca]

Steps to reprouce:

1. Activate Firefox Klar as content blocker for Safari
2. Go to Focus Settings and enable "Block Web Fonts" option
3. Open Safari and go to https://www.flimmo.de

See:

Recommendation:

• Add a message similar to Firefox, informing the users that enabling "Block Web Fonts" may break some pages.

Screenshot:

Note:

• From issue Firefox Klar Content Blocker on iPad Safari blocks font swapping  #1889