feat: add subtitle toggle hotkey

[schembriaiden]

Pull Request Description

This pull request introduces a new "toggle subtitles" hotkey feature to the video player, allowing users to quickly enable or disable subtitles using a keyboard shortcut. The implementation includes localization, hotkey mapping, and logic for toggling subtitles, including handling multiple subtitle tracks and remembering the user's last selection.

New Subtitle Toggle Feature:

• Added a new toggleSubtitles hotkey to the VideoHotKeys enum, mapped by default to the "T" key (LogicalKeyboardKey.keyT).
• Implemented the _toggleSubtitles method in _DesktopControlsState to handle toggling subtitles on/off, supporting both single and multiple subtitle tracks and remembering the last selected subtitle.
• Integrated the new hotkey into the video player controls so pressing the hotkey triggers subtitle toggling.

Localization:

• Added the toggleSubtitles string to the English localization file (app_en.arb) for display in the UI and settings.
• Updated the VideoHotKeys label mapping to include the new toggleSubtitles key for proper display in settings menus.

Codebase Maintenance:

• Added the necessary import for media_streams_model.dart to support subtitle toggling logic.
• Introduced a _lastSelectedSubtitleIndex state variable to remember the user's last subtitle choice across toggles.

Logic is as follow:

Press toggle:

1. If there is only 1 type of subtitle it just uses it
2. If there is multiple subtitle types:
   1. First time it asks you to select the one you want
   2. After it keeps using the same one.

Issue Being Fixed

Resolves #957

Screenshots / Recordings

Tested On

• Android
• Android TV
• iOS
• Linux
• Windows
• macOS
• Web

Checklist

• If a new package was added, did you ensure it works for all supported platforms? Is the package well maintained
• Check that any changes are related to the issue at hand.

[PartyDonut]

It seems to not work entirely like expected.

When I have a subtitle selected it still opens the subselection.
After then selecting that subtitle it toggles on/off fine.

When off is the initial selection and I press the toggle it shows subselection. After selecting something toggling works like expected.

But after then selecting a different subtitle toggling still toggles between the initial selection and off. Not the new selection and off.

[schembriaiden]

All the cases you mentioned should be fixed now.