Allow a font whitelist to be configured

[qgustavor]

This is just a feature proposal. I don't know if it's easy or hard to implement. Maybe it's easy, I don't know.

Background: often some translators use some fonts that cause issues and, no matter how hard those are educated not to use those fonts, once in a while they forget it. By using using a font whitelist this issue can be reduced a lot.

Proposal: allow a font whitelist to be configurable. This whitelist may just hide non-whitelisted fonts in the font selector, or not render those, what you think is easier (or best) to implement. This configuration doesn't need a UI as, at least how I think it can work, this configuration is provided to the translators along a portable Aegisub build.

Alternative ideas: if it's hard to be implemented in the fork like proposed then other solution would be making a private fork with a hardcoded whitelist. In the other hand, if there are other people having the same issues, making it a configuration would be better as each group can adjust it as their needs. Also I think adding a blacklist of fonts would not be a good idea as this list would be harder to maintain.

[Ristellise]

It should be possible but I'm not really in to editing UI to add new features. Hardcoded whitelist sounds really hacky to me.

I feel like this is really an odd use case that I think wont get much benefit. Even I add it, I dont think anyone would notice it either.