feat: add support for local cache to at_cli

[xavierchanth]

- What I did

• Added sync as a "verb"
• Added config and flags for --cache (boolean) and --cache-dir (string)

- How I did it

- How to verify it

Using those features here: https://github.com/XavierChanth/dotfiles/blob/trunk/dotfiles/dot-local/bin/at_pass

- Description for the changelog feat: add support for local cache to at_cli