preview-tui: add QuickLook support for WSL

[luukvbaal]

Add QuickLook support for WSL as suggested in #959.

Perhaps this should be a separate plugin since essentially bypasses all logic provided by preview-tui but on the other hand having all previewers in a single script has merit.

[jtourlamain]

@luukvbaal wow that was quick! When launching the preview, nnn returns to the command prompt but the preview windows opens. When hitting CTRL-C I return to nnn and the preview window functions as desired. Is there a way to disable the preview again, because if I close the preview window and select another file, the preview reopens.

[luukvbaal]

When not running in tmux QuickLook will be used to preview everything. I also added QuickLook as an additional option for preview_image so preview-tui(-ext) will now use QuickLook to preview images when running in tmux.

@jtourlamain not sure how to address the fact that you can't disable previews for the pure QuickLook preview mode. When running inside tmux, closing the preview pane will also stop QuickLook previews.

[luukvbaal]

As far as I'm concerned this can be merged.

The QuickLook and $TERMINAL preview modes could use a solution to kill the preview process when pressing ^C in nnn but I couldn't find a reliable way to do that in the script. We need a way to kill all child processes from a trap in the main plugin shell while not blocking nnn input but I couldn't figure it out.

[jtourlamain]

ok great thx

[jarun]

Thank you!

[luukvbaal]

Is there a way to disable the preview again, because if I close the preview window and select another file, the preview reopens.

@jtourlamain #961 allows you to do this by pressing the plugin key a second time.

[jtourlamain]

your implementation works like magic! I can start the previewer and stop it with the same command 👍
I can now use the Windows Terminal open up WSL2 browse my files with nnn and preview them with QuickLook.... nice!