Improve RedisSettings explanation in main_demo.py (#422)

Co-authored-by: Samuel Colvin <s@muelcolvin.com>

docs/examples/main_demo.py

@@ -3,6 +3,10 @@
 from arq import create_pool
 from arq.connections import RedisSettings
 
+# Here you can configure the Redis connection.
+# The default is to connect to localhost:6379, no password.
+REDIS_SETTINGS = RedisSettings()
+
 async def download_content(ctx, url):
     session: AsyncClient = ctx['session']
     response = await session.get(url)
@@ -16,17 +20,19 @@ async def shutdown(ctx):
     await ctx['session'].aclose()
 
 async def main():
-    redis = await create_pool(RedisSettings())
+    redis = await create_pool(REDIS_SETTINGS)
     for url in ('https://facebook.com', 'https://microsoft.com', 'https://github.com'):
         await redis.enqueue_job('download_content', url)
 
 # WorkerSettings defines the settings to use when creating the work,
-# it's used by the arq cli.
-# For a list of available settings, see https://arq-docs.helpmanual.io/#arq.worker.Worker
+# It's used by the arq CLI.
+# redis_settings might be ommitted here if using the default settings
+# For a list of all available settings, see https://arq-docs.helpmanual.io/#arq.worker.Worker
 class WorkerSettings:
     functions = [download_content]
     on_startup = startup
     on_shutdown = shutdown
+    redis_settings = REDIS_SETTINGS
 
 if __name__ == '__main__':
     asyncio.run(main())