Terminal file manager nnn brings previews, find and list, persistent session

This release has one of the most wanted features so far - preview hovered. The relevant wiki page has the details on the implementation and usage.

Find & list would let you search in your favourite subtree search utility (find/fd/grep/ripgrep/fzf) from `nnn` and list the results in `nnn` for working with them.

Persistent sessions ensure you always start where you quit `nnn`.

Plugins went through lots of improvements. Plugins which communicate back to `nnn` have a specification now (and it can be easily extended).

Lots of usability improvements and some good fixes.

Hope you enjoy `nnn` as much as we enjoy developing it!