[docs] Draft guidelines for what constitutes a community

Since there is no clarity on what is considered "acceptable" for listing on the open source communities database, a guide detailing this would be helpful.

Some general categories that cannot be listed on the database:

- Projects (open source or proprietary)
- Local/global conferences
- Slack/Discord/Zulip/IRC links -> While these can be supplementary links where the virtual communities gather, there needs to be a dedicated page for the virtual and in-person community events hosted by the community. (For example, [the zh-cn chapter of the TODO Group](https://community.linuxfoundation.org/ospo-local-meetup-china-zh-cn-speaking/))
- Product/proprietary software/hardware communities

Note: This document is intended to be an iterative process, rather than a one-time effort.