Recognise color tags and style them appropriately

[hikari-no-yume]

[JosJuice]

If we're going to have a feature like this, I think our parsing rules should try to match the parsing rules of some playback program. The parsing rules you currently have don't actually match any playback program as far as I know, they just happen to match Soramimi and ECHO in one common case. (Soramimi only supports colors at the very beginning of a line as far as I know, and ECHO has additional ways of setting colors that aren't included in your rules. But I don't believe either of these programs have documented their color parsing rules, so perfectly matching them would be hard.)

Additionally, it should probably be possible to disable this feature, in case someone sets a color that makes the text hard to read. But that would have to wait until we have a settings window...

[hikari-no-yume]

I pushed a new commit that matches Soramimi's parsing of color tags as precisely as possible without supporting subtitle=true, though I guess I didn't ensure they can only occur at the start of a line.