[Feature Request]: hold Spacebar in Player to temporarily change playback rate until unpressed

### 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

yt has recently added this feature to their player that when you hold spacebar, video temporarily speeds up until you unpress it
would be neat to have this feature in freetube's player too, maybe give an option to customise the desired playback rate in Player settings too

### Proposed Solution

add this feature since current spacebar hold behaviour is pausing and unpausing video which i doubt a lot of people find useful, unlike the proposed feature

### Alternatives Considered

None.

### Issue Labels

new feature

### Additional Information

for correct behaviour check yt's player implementation

Start by locating the Player's Spacebar handling and the Player settings entry points; compare the intended interaction with YouTube's player implementation. Done means holding Spacebar temporarily changes playback rate, releasing it restores the prior rate, and the existing pause behavior is addressed; clarify whether a customizable rate is required.

Written by the indexing model from the issue text.