Ignore BBCode for RichTextLabel auto translate

[Joy-less]

As far as I know, the only easy way to center a RichTextLabel is to use the [center] BBCode tag:

[center]Text

However, this means Text won't be auto-translated unless the translation table includes the [center] tag.
Tags aren't rendered, so they should be excluded from auto translation.

[Calinou]

In this case, I recommend concatenating the text with a script as follows:

func _ready() -> void:
	text = "[center]" + tr("Text")

Either way, I feel having a default alignment property in RichTextLabel would make more sense.