Text box editing widgets

[NathanLovato]

Pitch

Create an add-on widget to edit and format text more efficiently in Godot.

Problem

I'd like us to produce more tutorials and sometimes have text on screen, or to create rich slideshows. Having to switch to external bbcode editors all the time is a pain.

Also, the RichTextLabel and TextEdit nodes don't work like paragraphs or containers in html, so using an external editor, you still have to copy the text over to Godot to see if it looks good.

To work productively, I need to be able to:

• Wrap selected text with bbcode tags or to remove them: bold, italic, and color only to start with.
• Force the text box (RichTextLabel or TextEdit) to resize based on its content
• Undo any operation

That would cover all the bulk of the time-consuming work I had to do formatting text on Godot slides and the GDScript tutorial.

We could then reuse this along with the GDquest theme and other widgets in all our tutorials.

Tasks

1. #28 Resize text boxes button
2. #29 BBCode editor