Add the image preview feature with viuer

[kyoheiu]

From #183, #188

• Native support for the image preview with viuer
• Efficient preview of gif image using gif crate

[kyoheiu]

viuer's sixel feature does not work on runtime because sixel-sys doesn't provide its own compiled libsixel library: cf. AdnoC/sixel-sys#3
This library seems unmaintained for years.

[kyoheiu]

I leave this PR open until the issue above is solved.

[kyoheiu]

Refactored the image preview flow: Now it is supported by default, and if your terminal implements iTerm protocol (i.e. Wezterm) it can show the high-res image.
Furthermore, if your terminal supports sixel or kitty protocol, by installing chafa you have the high-res preview.