[FEATURE] Pinned messages (nip51, event 10001)

[davotoula]

As an amethyst app user I would like to see pinned messages by other users and be able to pin (one of?) my messages on my profile.

So that I can see content pinned by other users and be able to highlight some of my own content for others to see.

Describe the solution you'd like Display any pinned messages when clicking on another user's profile

Display "pin message" when selecting one of my own messages.

Allow multiple messages to be pinned if nip51 supports it.