[Feature Request]: Quick Settings Menu

### 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

There are certain settings that are tinkered with more regularly, like the current Invidious instance, region for trending, proxy settings, and base theme. Changing routes just to change these can be quite an onerous journey, though. And even if we do ever have t*bs, that change-settings flow is still its own journey that you have to go out of your way to embark upon.

### Proposed Solution

Implement a quick settings menu for changing the most used settings. What those settings should be by default will always be up for debate & will vary based on the UX of this specific implementation. In the interest of getting things out, customization of the displayed settings are out of the scope for this issue. Also, in the interest of starting the discussion, here are my opinions on what those default quick settings should include:
- Preferred API Backend
- Hide Videos on Watch
- Base Theme
- Show Keyboard Shortcuts
- (Contingent on available space) Primary & Secondary Color Themes

This does introduce a new question of whether the user should be prompted to enter their chosen password every single time that they open the quick settings. I think you can make a convincing answer for both, depending on which settings are included. Our options are:
1. Don't put a lock on these because they're less important - no permanent data deletion or overwrite (at the cost of allowing anyone to change these)
2. Do put a lock on these because they may be considered important (at the cost of it being more tedious to use)
3. Put an option to put a lock on these (at the cost of growing our ever-expanding Settings)

I would personally be fine with 1 or 3 (with lock disabled by default).

As for the UX of the control itself, it would make sense for it to be a "More Options" button near the Profile Selector icon that opens either a dropdown-ish item and/or a modal dialog box ("and/or" if it becomes a modal dialog box on smaller device sizes).

### Alternatives Considered

Don't implement this feature.

### Issue Labels

ease of use improvement, improvement to existing feature

### Additional Information

For context, here's YT's take on it: