Add hidden "advanced" section to enter data urls as resource

[AlexandreSi]

Closes #3984

[4ian]

This is a new feature that we engage ourselves to support forever, so an additional multiplier to the complexity of the resource management. I'm ok with this if we display a warning and maybe even refuse anything larger than X kb. Otherwise, Murphy's law/big number law, we will end up with people stuffing 1MB+ resources in their game and complaining "why did GDevelop/my browser/the backend crashed?"

[AlexandreSi]

I thought it was supported but not clear how to use.

In that case, maybe it's better not merging that and just answering to the issue that this is a hack that works but that might break in the future (but hopefully it won't be needed in the future).

[4ian]

Yes, I've commented on the thread! Let's hold this then, unless we get massive support for this or that we decide it's reasonable to support this officially.