HTML Source Editor for INKY Email Signatures

Currently, signatures are created using the visual Layout Builder. It would be very useful to have the option to view and edit the complete HTML source code of a signature, similar to CodeTwo.

Ideally, we would also like to be able to import or paste an existing HTML signature template. This would provide more control over custom layouts, spacing and styling, while making it much faster to migrate existing signatures without having to rebuild them manually.