Put overall maintenance checker results in README, on a cron

[sarina]

• Run the maintenance_chart_checker (feat: Add script for reporting maintenance chart pass/fail coverage #1008 ) and put the results in the README, under the Submit Documentation Issues header
• Put the script on a biweekly cron job that:
  • Runs the script
  • Opens a PR to put the output into the README

[sarina]

This is prior art that may be helpful: https://github.com/eduNEXT/openedx-events-filters-analysis/blob/reports/.github/workflows/reports.yml