Organise 'tools' modules into a subpackage

src/mpd_now_playable/tools/asyncio.py

@@ -0,0 +1,19 @@
+import asyncio
+from collections.abc import Coroutine
+from contextvars import Context
+from typing import Optional
+
+__all__ = ("run_background_task",)
+
+background_tasks: set[asyncio.Task[None]] = set()
+
+
+def run_background_task(
+	coro: Coroutine[None, None, None],
+	*,
+	name: Optional[str] = None,
+	context: Optional[Context] = None,
+) -> None:
+	task = asyncio.create_task(coro, name=name, context=context)
+	background_tasks.add(task)
+	task.add_done_callback(background_tasks.discard)