Add clarity in documentation for editing sync.yml when permissions don't allow editing the file

[kweav]

There are reports that people outside of the organization or who don't have necessary permissions can't edit sync.yml files and so going to clarify in documentation what to do in those cases, such as

• Clarify that you can open an issue asking us to add you to the sync.yml
• Create an issue template for that case above ^
• Clarify what you can do so that you can fork and edit

[kweav]

a PR in the ottrproject.org repo addresses the first and last bullet point above. A PR in this repo will address the 2nd one shortly