compose-sheet: Rework to be a bottom sheet

Author: kra-mo

openemail/__init__.py.in

@@ -21,6 +21,9 @@ from openemail.core import client
 if TYPE_CHECKING:
     from asyncio import Task
 
+    from openemail.widgets.compose_sheet import ComposeSheet
+
+
 APP_ID = "@APP_ID@"
 VERSION = "@VERSION@"
 PREFIX = "@PREFIX@"
@@ -32,6 +35,8 @@ secret_service = f"{APP_ID}.Keys"
 log_file = Path(GLib.get_user_state_dir(), "openemail.log")
 client.data_dir = Path(GLib.get_user_data_dir(), "openemail")
 
+compose_sheet: "ComposeSheet"
+
 
 class Notifier(GObject.Object):
     """Used for sending user-facing information throughout the application."""