T22 round 1 fixes

- a remote cursor shows only while its caret sits inside the field, sideways too
- presence avatars keep a transparent border for the focus ring
- the access list shows each role, as words when it cannot change
- status dots take the theme's size
- peer and member pictures load from files and web addresses alike

src/documents/mod.rs

@@ -25,6 +25,7 @@ mod viewer;
 
 use gpui::App;
 
+pub(crate) use blocks::source;
 pub use blocks::{Align, BlockData, BlockEditor, BlockEvent, BlockKind, Media};
 pub use counts::{ReadingTime, WordCount};
 pub use epub::{Chapter, EpubReader};