Add inline relation marks (for internal linking)

[formfcw]

In addition to relation blocks it would be nice to integrate relation marks. This would cover the use case for internal linking.

A user could select text and then relate to a M2A item.

[jdjoshuadavison]

Was about to submit a new feature request for this exact functionality.

[erichjsonfosse]

This would be very nice, yes.

@formfcw Let me know if there's anything I can do to help!

[formfcw]

Thank you for your offer. I am planning a complete rewrite of the relationship thing. I may let you know when I've done the groundwork and I am ready to accept contributions for this feature.