feature: improve the captions settings ui and add keyboard shortcuts to change font size

[Gourav-21]

Current UI
The settings of caption looks really bad and there is no shortcut to change the size of fonts while watching the video, i have to open the settings everytime to change the size.

Suggestions

• improve the ui of caption settings
• add shortcuts to change size of font like its on youtube using - and +
• and add support for numpad to go forward and backward in video

[shahkashish]

To tackle the 2nd enhancement i.e. "add shortcuts to change size of font like its on youtube using - and +", we will have to

1. Add a State for current Subtitle Font Size.
2. Attach a keydown event listener to the component to capture the + and - keys.
3. Dynamically adjust the font size of the subtitles according to the current state of subtitle and the key that is pressed.
   above steps would let us complete the task

[shahkashish]

If you like the approach lmk and i'll start working on it, even if you have different views you can tell me.

[Gourav-21]

@shahkashish yeah please go on

[shahkashish]

could you assign it to me?
as it is mentioned that task should be assigned first and then i have to make PR