With reference to #8025, this is a partial proposal to see if this style
of extensible customisation could be favourable to the shaka-player
community:
Proposal for some accessibility options whereby an App builder can
customise subtitle/caption size, with the potential of an App offering
accessibility options for text size.
This style could be used for other text styling attributes in a similar
way, but this is just the first step.
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Co-authored-by: Álvaro Velad Galván <ladvan91@hotmail.com>