window: translate_selection: Only get clipboard when window is active

[rafaelmardojai]

Fixes #407

[mufeedali]

The fix itself works. But wouldn't it make more sense to split the two modes of operation of translate_selection() into two functions? Something like queue_selection_translation and translate_selection maybe?

[zefr0x]

I'm not sure about the UX, should we also have a visual indicator?

Maybe an AdwStatusPage with an arrow icon that covers every thing asking for focus or some thing like that.

[rafaelmardojai]

The fix itself works. But wouldn't it make more sense to split the two modes of operation of translate_selection() into two functions? Something like queue_selection_translation and translate_selection maybe?

Done, code should be cleaner.

I also made selection_translation_queued a GObject property so it can be binded to UI if we implement what @zefr0x suggests. (Maybe not needed depending on how we do that implementation, but just in case 😅)