sysutils/nnn: Update to 3.6

Changes:
- REPL command prompt (Esc or Enter to exit)
- invert selection with A
- option -u removed (always prefer selection to hovered)
- visit start dir on @ when start path is a file
- exit filter mode and redraw on ^L if no last filter
- plugin `fzcd` now selects the chosen file (#876)
- `ueberzug` support in plugin `preview-tui`
- new plugin `preview-tui-ext` with extra preview support
- clear selection after successful plugin invocation
- add method to sync subshell `$PWD` in WIki
- clear selection on single file deletion (#812)
- copy between instances not working (#864)
- plugin `togglex` to toggle exe mode of a selection (#813)
- fix `memccpy()` buffer overlap fault on macOS (#786)
- show `0 selected` msg on cp/mv with empty selection (#855)
- fix frozen terminal caused by opener (#858)
- migrate macOS CI to GitHub workflows, retire Travis

(sjmulder)