Add integration with github webhooks

[pmakowski23]

Use octokit/webhooks.js

• get available channels from the database
  • create slash command after each update of guild related projects
  • create if not exists channel for GitHub integration (shortname-github)
• command to create GitHub integration with
  • GitHub webhook secret
  • not reviewed PRs reminder intervals (cron)
  • role to mention with reminder
  • project you want integration with
  • do you want checks error info
• bot will send
  • custom messages on pull requests
  • add reactions based on actions connected with PR
    • ✅ on approval
    • ♻️ on requested changes
    • 📝 on added comment
    • ❌ on any of the checks result in error
  • send message on pull request merged
  • send reminders (based on interval)