Migrate karabiner-elements from Homebrew to Nix

[delafthi]

Migrate karabiner-elements from Homebrew cask to Nix package.

Blocking reason: Broken in nix-darwin

The nix-darwin service module for karabiner-elements is currently broken. See upstream issue: nix-darwin/nix-darwin#1041

Possible solutions:

• Wait for upstream fix in nix-darwin
• Investigate and contribute a fix to nix-darwin
• Use nix-darwin homebrew module (current workaround)

Parent issue: #92

[delafthi]

Successfully migrated to Nix! This package is no longer in the Homebrew configuration.

[delafthi]

Reverted migration due to broken nix-darwin service module. See nix-darwin/nix-darwin#1041 for details.

[delafthi]

Best would be to migrate to kanata a crossplatform alternative. Though, a nix-darwin implementation is still open.