This reduces the size of the editor binaries significantly, as we otherwise
embed all WIP translations, including ones with very low completion ratios,
and end up paying for the size of all `msgid`s for each locale.
Cf. https://github.com/godotengine/godot-proposals/issues/3421 for details.
The thresholds used are:
- 30% for the editor interface (should already include most common strings
while more obscure ones like UndoRedo action names might be untranslated).
- 10% for the class reference: this is a HUGE resource and 10% is already
a lot of useful content, especially if focused on the most used APIs.
For 3.x, we also exclude languages that require complex text layout support
to be displayed properly.
This currently reduces the size of the editor binary by 17% on Linux.
The list will be synced manually every now and then.
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