Add webhook when creating read-only GH mirrors which closes PRs

Fix #80 (closed)

.gitlab/issue_templates/New Official Project.md

@@ -85,6 +85,11 @@ If you want to add a new official project, here are some guidelines to follow:
    - `Wiki`
    - `Issues`
    - `Projects`
+1. [ ] Go to https://github.com/archlinux/my-example/settings/hooks and add a new webhook
+   - `Payload URL`: `$(misc/get_key.py misc/vault_github.yml github_pull_closer_webhook_url)`
+   - `Content type`: `application/json`
+   - `Which events would you like to trigger this webhook?`
+     - `Let me select individual events.`: `Pull requests`
 1. [ ] In the GitHub description of the mirrored project, append " (read-only mirror)" so that people know it's a mirror.
 1. [ ] Disable `Packages` and `Environments` from being shown on the main page.
 1. [ ] In the website field put the full url to the repository on our GitLab.