feat(twitch): force HD video

[smartinio]

Proposed changes

Adds a Twitch player setting, Force HD Video, that automatically selects the highest available quality for any active stream.

Fixes #628 by using Twitch's player quality API to prefer the best available variant and to prefer Source when multiple entries share the same displayed quality.

Types of changes

What types of changes does your code introduce to 7TV?
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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

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• I have read the CONTRIBUTING doc
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged