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This allows selecting either the monitor or the window again,
without having to remove and readd the source.

Only 3 strings, and translated to Brazilian Portuguese as well,
because I want :)

It is desktop-only, so move it to the appropriatedly named file.

And make it desktop only for now.

This code will be shared when the big split between window
and desktop capture happens.

Instead of using GStreamer, use PipeWire directly.

Not everyone has an updated GLib for that.

This is a bit broken right now on GNOME Shell / Mutter side,
but it should still be okay since window instrospection is
hidden behind a GSetting anyway.

Add the same prefix everywhere, remove useless ones.

Introduces the plugin, which itself depends on GStreamer,
GDBus, and GLib in general.