Feature request: Bring window to front

[Jordatious]

It would be useful to enable the user to click on a window to bring it in front of the others. e.g. if I open the header, then the contour config, the latter opens behind the former. I think it's sometimes/often useful to have the file browser open on top of everything, but generally, I think the user should be able to choose which window is at the top simply by clicking on it. Obviously it's best to pin widgets, but some users won't want that, particularly for temporary windows / dialogues like the header, file browser, and perhaps the contour config.

This is a generalised issue partially solved by CARTAvis/carta-frontend#1336.