Create a document to explain our Community Open Sessions

## Description

I want to explain our Open Sessions and make it clear that these:
- are open to anyone to attend
- no need for video camera usage, it's usually audio only
- opportunity to meet some leaders and ask questions and debug together
- may happen on Google Meet or Zoom
- link the calendar in multiple timezones
- ???

## Acceptance Criteria
### Update [Required]
- [ ] Add new document to explain our Community Open Sessions
- [ ] Add the document link to Documentation section on the README

## Definition of Done
- [ ] All of the required items are completed.
- [x] Approval by 1 mentor.

## Estimation

0.5