Add meson example

[svenstaro]

Hey, rofi itself now also uses meson and I think it'd be neat if you could extend this template to also feature meson support. The plugin guide should then also be adjusted.

[DaveDavenport]

I've used this previously: https://git.sr.ht/~qball/rofi-linkding/tree/master/item/meson.build

Not sure when I have time to update this.