Shell tab-completion scripts

[djdarcy]

Summary

Add shell tab-completion scripts for bash, zsh, fish, and PowerShell.

Proposed Completions

teeclip --<TAB>
# --paste --append --backend --no-clipboard --quiet --version --list --get --clear --save --config

teeclip --backend <TAB>
# windows  macos  xclip  xsel  wayland  wsl

teeclip --get <TAB>
# 1  2  3  4  5  (from history)

Implementation Options

1. Static scripts: Ship pre-written completion files in completions/
2. argcomplete: Add argcomplete as optional dependency for automatic argparse completions
3. Generated: teeclip --completions bash outputs the script for users to source

Delivery

• pip install teeclip[completions] for argcomplete-based
• Or include static scripts and document sourcing in README

Related

• Roadmap Phase 3 (Roadmap — teeclip #1)