Reports.md: describe how we handle received reports

[olasitarska]

• Information about rotation duty and how it is implemented
• What kind of reports we receive
  • From local reps
  • From people asking for help
• If response requires decision, we aim to respond with a quick acknolwedgment of received report in a couple of hours
  • Add example response here -- we may use the last one I sent last weekend
• If response doesn't require decision, we still aim to respond within couple of hours, but acknowledge the report, thank the reporter, say we're gonna keep it on file.