This PR also adds default font styles for RichTextLabels
in the editor, and improves the introduction dialog
when you don't have any local projects available.
The offline mode is implemented in the asset library
plugin, alongside some code improvements.
This change introduces a new EditorThemeManager class
to abstract theme generatio and its subroutines.
Logic related to EditorTheme, EditorColorMap, and editor
icons has been extracted into their respective files with
includes cleaned up.
All related files have been moved to a separate folder to
better scope them in the project. This includes relevant
generated files as well.
