columns: switch to bitflag app options

we're adding a ScrollToTop bool for an updating change
to the toolbar, but we have too many flags now. Let's switch
to bitflags

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

crates/notedeck_columns/src/lib.rs

@@ -17,6 +17,7 @@ pub mod login_manager;
 mod media_upload;
 mod multi_subscriber;
 mod nav;
+pub mod options;
 mod post;
 mod profile;
 mod route;