Add a `status` option or similar for listing dependencies

[Dave Shoreman]

Output a list of dependencies and whether or not they're installed, similar to :call phpactor#Status() in vim. Option should be something like --status or --deps.

It could also show output of $(nextshot --version), but dependencies should be limited to the detected environment. In other words, don't show Wayland deps if X is detected, and vice versa.

Example Output

Current version: NextShot v1.2.3
Detected environment: Wayland

Dependencies
------------
✔ curl
✘ grim
✔ jq
✔ slurp
✔ wl-clipboard
✘ yad (optional)