Add settings option to graphically set compose key

### Feature Description

I think that a graphical option in the settings menu for setting a [compose key](https://en.wikipedia.org/wiki/Compose_key) (like KDE) would be really useful because it's a lot more convenient than editing a compositor config.

### Use Case

This is useful for people who frequently type in different languages using Latin script, do not want to switch keyboard layouts unless necessary, and want to quickly set the compose key without delving into configs.

### Compositor(s)

All compositors

### If Other, please specify

_No response_

### Proposed Solution

I think the best existing place to put such an option would be the the Keyboard Shortcuts menu.

### Alternatives/Existing Solutions

Most compositors include a way to set compose key in their config.