See https://github.com/godotengine/godot/pull/23658#issuecomment-562706669
The method was implemented back when Dictionary.get(key, default) did not
exist, but now that it does we do not need a custom method in CharFXTransform.
It's a new feature in 3.2, so does not break compat with 3.1.x.
Added a new ItemFX type to RichTextLabel which supports dynamic text
effects.
RichTextEffect Resource Type was added which can be extended for more
real time text effects.