Caption font size adjustment

[hiroshisuga]

Is your feature request related to a problem? Please describe.
Sometimes a chunk of transcription text is so large that the caption covers almost the whole presentation.

Describe the solution you'd like
Implementing a caption font size button on the toolbar. With it the users would be able to adjust the font size as they wish.

Describe alternatives you've considered
Automatically adjust the font size depending on the amount of text that need to be shown.

Additional context
Caption font size adjustment seems to have been removed from a live meeting of BBB as well (since BBB 2.7?).