ui: add initial Profile hover previews

The idea with these is that on notedeck you can just hover your cursor
over a profile link to see the profile. I just have a stub for now, but
full design coming soon after.

Also simplify the preview system even further with a macro. In the
future I imagine we can grep every preview in the codebase, and then
include this as a string inside this macro. This is some kind of
template metaprogramming insanity but in theory it could work.

Signed-off-by: William Casarin <jb55@jb55.com>

src/ui/note/mod.rs

@@ -106,7 +106,7 @@ impl<'a> Note<'a> {
                 match profile
                     .as_ref()
                     .ok()
-                    .and_then(|p| p.record.profile()?.picture())
+                    .and_then(|p| p.record().profile()?.picture())
                 {
                     // these have different lifetimes and types,
                     // so the calls must be separate