Add APScheduler as builtin scheduler

setup.py

@@ -15,6 +15,9 @@ setup(
     long_description=long_description,
     long_description_content_type='text/markdown',
     install_requires=['aiocqhttp>=0.6', 'aiocache>=0.10'],
+    extras_require={
+        'Scheduler': ['apscheduler>=1.2'],
+    },
     python_requires='>=3.6',
     platforms='any',
     classifiers=(