Tweak copyProfileUrl to give user a shareable link where the user's profile can be viewed

[rjcorwin]

When I first started using Fritter, I got stuck trying to figure out how to share my fritter profile and how other users would subscribe to me. This PR will result in the copied profile URL going from a copied URL of dat://a8d566b635fd219085a0c7e9e9c57f5bed3e6717eca230883631b8079fae4bba to dat://fritter.hashbase.io/user/a8d566b635fd219085a0c7e9e9c57f5bed3e6717eca230883631b8079fae4bba which is something I can share. This seems like the expected behavior to me, I won't take offense if that's not the case for others in which case this PR can be closed.

Related: https://github.com/beakerbrowser/fritter/issues/36