[Feature Request]: Captions Styling options

### Guidelines

- [X] I have searched the issue tracker for [open](https://github.com/FreeTubeApp/FreeTube/issues?q=is%3Aopen+is%3Aissue) and [closed](https://github.com/FreeTubeApp/FreeTube/issues?q=is%3Aissue+is%3Aclosed) issues that are similar to the feature request I want to file, without success.
- [X] I have searched the [documentation](https://docs.freetubeapp.io/) 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

First let me thank you all for the time and effort put into the app. The latest update was amazing! The new player looks and feels great!!
I know is just brand new and mostly the work of a single chad (thank you @absidue!) and you'll all continue to improve it as time goes on.

This time seems the new captions don't support any kind of styling. The current default one is white text with a black background. While might work wonders for reading, not so much for enjoying that subtitle with video. It might already be in the to-do list but I really miss the white text with black edge or shadow.

Thanks again for the love and care for the app. Wish you the best in life. Have a wonderful day!!!

### Proposed Solution

Styling options like color, shadow, contour and size.

### Alternatives Considered

Using the previous version if really necesary

### Issue Labels

improvement to existing feature, visual improvement

### Additional Information

_No response_