typo and broken links

[realsobek]

I hope this is the correct location to report these issues:

1. On https://owncloud.com/virtual-file-system/ in the "The Virtual File System in action." section you can read "Files with a green checkmark have been synced locally while a cloud, icon indicates a virtual file." Please remove the comma.
2. On https://owncloud.com/docs-guides in the "Manual" tile all 3 links lead to "Page Not Found":
   For system administration
   For users
   For developers
3. On https://central.owncloud.org/t/i-want-to-report-a-bug-for-owncloud/829 broken link: https://github.com/owncloud/core/blob/master/CONTRIBUTING.md
   I am not sure which one it should be:
   https://github.com/owncloud/core/tree/master?tab=readme-ov-file#contribution-guidelines
   https://github.com/owncloud/core/tree/master?tab=contributing-ov-file