Respect user's fonts

[Gitoffthelawn]

Before submitting your pull request

• I agree to license my code under the MPL 2.0 license.
• I rebased my work on top of the main branch.
• I ran npm test and all tests passed (well, it fails without this PR, so that's a different issue).
• I added test coverages if relevant.

Description

Firefox Multi-Account Containers does not use the user's fonts. This is a problem for multiple reasons, including:

1. Creates an unneeded accessibility issue
2. Violates user's expectations
3. Increases bloat (increases RAM usage, increases storage requirements, decreases Firefox launch performance)

Type of change

Select all that apply.

• Bug fix
• New feature
• Major change (fix or feature that would cause existing functionality to work differently than in the current version)

Tag issues related to this pull request:

Issue #2891