[Feature Request] Make video subtitles selectable

Guidelines

[X] I have searched the issue tracker for open and closed issues that are similar to the feature request I want to file, without success.
[X] I have searched the documentation for information that matches the description of the feature request I want to file, without success.
[X] This issue contains only one feature request.

Problem Description

Video subtitles are not selectable. Making it selectable should be a minimal change, and would be very helpful for language learners who want to look up words or translate sentences.

Proposed Solution

Set the text to selectable. I think it would be fine for it to just be the new behavior, but it would be fine to make it an option as well.

Alternatives Considered

In browsers, there are various extensions to make them selectable, but they are not available for use in freetube.

Issue Labels

ease of use improvement

Additional Information

No response

FreeTubeApp / FreeTube