[Feature Request]: Add a proxy option/support for `.pac` file

### 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

Please add a proxy option/support for auto-configuration `.pac` file

### Proposed Solution

Text field there you can put the url to pac file, e.g.:
`https://antizapret.prostovpn.org/proxy.pac`
`file:///home/user/proxy_file.pac`

### Alternatives Considered

inline script in pac format

### Issue Labels

improvement to existing feature

### Additional Information

_No response_