grimblast: only allow one instance

[fufexan]

Description of changes

Allow only one instance of grimblast to be active at a time. Fixes #112

Things done

• For new programs

  • Add the program to the README table, with yourself as the
    maintainer
  • Add a README for the program itself
  • Add Makefile (and Nix derivation optionally, otherwise @fufexan will do
    it)
  • If the program is a script, add it to the
    CI checks matrix

• For changes

  • Add changes to the CHANGELOG

[fufexan]

@DHDcc can you test this?

[DHDcc]

@fufexan it works IF I don't spam my keybind:

No spaming:
https://github.com/user-attachments/assets/ad69f75a-9d44-4c5d-ace3-ffff9a93f179

Spaming:
https://github.com/user-attachments/assets/9d0e3d44-38ff-41e9-9197-4a531beb1246

Insted of having 10+ instances, I have 2 instances max (if I spam my keybind)

[fufexan]

Looks like I can't make grimblast only allow one instance of itself to be running from within itself. I've tried using lockfiles, but that doesn't work either. And pgrep seems too slow to be useful when called from within the script.

However, I have these binds in my hyprland config which work exceptionally well, even when spamming the key:

bind=, Print, exec, pgrep grimblast || grimblast --notify copysave area
bind=CTRL, Print, exec, pgrep grimblast || grimblast --notify --cursor copysave output
bind=ALT, Print, exec, pgrep grimblast || grimblast --notify --cursor copysave screen