cliphist optimizations

[boredland]

Following up with a closed thread on the forums, I'd like to add the following cliphist behaviour:

• Make cliphist an optional dependency
• Purge the history on middle-click on the icon
• Purge the history on shutdown
• add a menu to delete single items from the history

[Mathew-D]

To purge the history of cliphist you need to do the following:
rm ~/.cache/cliphist/db

Making optional is fine overall I just don't know how to make it optional for waybar

[Mathew-D]

Closed by manjaro-sway/desktop-settings#77