Log Message:
aerc: update to 0.20.1

Added:
- `copy-to now` supports multiple destination folders.
- All commands that involve composing messages (`:compose`,
  `:reply`, `:recall`, `:unsubscribe` and `:forward`) now have
  a new `-s` flag to skip opening the text editor and go directly
  to the review screen.

Fixed:
- `copy-to-replied` now properly works without having `copy-to`
also
set.
- `copy-to-replied` creates empty messages when `copy-to` is also
  set.
- The address-book completion popovers now again appear under the
  field being completed.
- The new-message bell is now rung again for threaded directories
  as well.
- `:sign` and `:encrypt` descriptions overflow the review screen.
- Some messages are hidden when using client side threading.

Changed:
- The `default` styleset status line background has been reset to
  the default color in order to make error, warning or success
  messages more readable.
- Key bindings in the compose review screen are now displayed in
  the order in which they are defined in the `[compose::review]`
  section of `binds.conf`.
- It is now possible to explicitly hide key bindings from the
  compose review screen by using a special ` # -` annotation.