fix: the inconsistency between the UI size and the screen size in the first frame

[Tobiichi-Origuchi]

After Plymouth finishes, when Tuigreet renders the first frame, the size of that frame (25,80 for my device) may not match the screen size (50,160 for my device), causing the UI to appear crammed into the top-left corner. It isn’t until the second frame (0.5 seconds later) that the correct size is obtained, and the UI is centered and displayed normally.

After Plymouth finishes, KMS will send a SIGWINCH. Having the UI redraw when this signal is received will resolve the issue.

[Tobiichi-Origuchi]

I'm not sure if this issue can be reproduced on other devices, but triggering a redraw after a TermEvent::Resize isn't any expensive operation in itself, while it ensures the rendering is correct.

[NotAShelf]

Bit of a weird issue, but the solution LGTM. Since I can't quite reproduce and test the fix, I'll merge this as is. Diff LGTM.

One thing I'll ask of you is to fix your commit message; this repository uses scoped commits and I'd like to avoid squashing to change the message.

[soupy-boy]

@NotAShelf it looks like the commit message has been fixed so you should be good to merge. Also, maybe we should make a Contributing.md explaining what we want commits in prs to look like?