Description of the new feature/enhancement

Many apps/tools nowadays provide shell completion files (for bash/zsh/powershell). They help in easy discovery of commandline arguments and are overall a QoL enhancement.

Since wt supports a plethora of commandline args, it'be pretty nice to have completion files for PowerShell and CMD (through Clink, if possible).

Proposed technical implementation details (optional)

All shells have their own way of defining completions. (For powershell it's Register-ArgumentCompleter).

Almost all CLI utilities provide the files (examples - ripgrep, gh (CLI), hyperfine). Alacritty, too provides completion files for bash, zsh and fish as a part of their release.