Update --help argument output

[ReenigneArcher]

https://github.com/SunshineStream/Sunshine/blob/4b658cd86ba0b7520f6f7cb5b5f07d6775845a81/sunshine/main.cpp#L62

Add a comment that the configuration file will be created automatically if it doesn't exist.

[github-actions]

This issue is stale because it has been open for 30 days with no activity. Remove the stale label or comment, otherwise this will be closed in 5 days.

[github-actions]

This issue has been fixed and will be available in the next release.