- Adds support for handling drawings as embeds, based on image
extension.
- Adds additional attribute to drawio elements within editor to prevent
tinymce replacing embeds with a placeholder.
- Updates how contenteditable is applied to drawio blocks within editor,
to use proper filters instead of using the SetContent event.
- Allowed DRAWIO env option to be passed as URL to point to instance.
- Updated tests to check URL gets passed to pages correctly.
- Update default URL to be the default theme.
For #826