feat: Are there solutions in KeymanWeb to let the user choose a better font if the given one has issues?

@merchako had this question from a Slack channel:

> are there solutions in KeymanWeb to let the user choose a better font if the given one has issues?
>
>In a usability test with a Sinhala translator last night ([video recording](https://drive.google.com/file/d/1cfSlRfNjeKzmQjrsx_-i8bvv-dEoDQsT/view?usp=sharing) at 32:50), the user had issues with the font displaying character combinations incorrectly (dotted circles). She knew specific fonts that work well, and she doesn’t have this issue when using Google Translate’s interface.
>
>Does Keyman provide any ways for the user to pick alternative fonts, or for the web developers to add additional fonts? I wasn’t able to find information about such a feature in the docs.


@mcdurdin replies:
> That sounds more like input order than font issues. Dotted circles appear when there is a letter that expects a base letter, for example a diacritic on a letter in Latin script.