[enhancement]: Change brush-size like in Photoshop

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Contact Details

info@nieschalk.com

### What should this feature add?

Add the possibility to interactively change brush-sizes in unified canvas with keyboard shortcut.

+ Hold alt+right mousebutton, then move left-right to change brush-size quickly and easily like in Photoshop. The current size should be previewed directly on the canvas to see if it fits.
+ Same would be good to change opacity, but with alt+right mousebutton and up-down-movement.

I've been missing this feature since the beginning, maybe because I'm so used to use it in Photoshop...

### Alternatives

_No response_

### Additional Content

_No response_