restrict-applications-dialog: Add support for searching the app list

This is a type-ahead search which filters the app list by app name.

It’s always visible because search is a very obvious interaction the user might want to do to find an app in the app list. That’s why GtkSearchBar is not being used here.

Signed-off-by: Philip Withnall pwithnall@endlessos.org

Fixes: #31 (closed)

Closes #31 (closed)