Improve zsh completion function
Improve zsh completion function

- Add missing options
- Fix confusion between --count and --max-count
- Improve wording consistency (capitalisation, punctuation, contractions, &c.)
- Add completion for encodings
- Add completion for colour specs
- Add partial completion for type specs

BurntSushi/ripgrep,BurntSushi/ripgrep,BurntSushi/ripgrep,BurntSushi/ripgrep