`.import` files (not to be confused with the `.import/` directory)
should be included in version control as they contain important
metadata, such as whether a texture should be filtered or not.
A `.gdignore` file was added to the `doc/` folder of the add-on,
which prevents Godot from importing any files inside.
This also speeds up the initial editor import step.
Added documentation for Material, Export, Comment, Switch and Remote nodes.
Fixed missing "tool" attribute in editable_label script.
Reordered misc. nodes in base library.
