Add notifications for target maintainers (#10)

This adds a feature where maintainers can add themselves to an array in the source to receive notifications whenever the target fails.

The way this works is via GitHub, I created a new repository https://github.com/Noratrieb/does-it-build-notifications where an app will create issues that ping the respective users. This is the easiest option for me and also fits nicely into people's workflows on GitHub.

Whenever a target fails, an issue is created for it. This issue is kept open (with a new comment every day that it continues to fail), and then closed when the target builds again.

README.md

@@ -12,9 +12,21 @@ It does this in parallel, using half of the available threads (or `DOES_IT_BUILD
 
 - `DB_PATH`: Path to SQlite DB to store the results
 - `DOES_IT_BUILD_PARALLEL_JOBS`: Parallel build jobs, defaults to cores/2.
+- `GITHUB_SEND_PINGS`: If this is set, actual pings will be sent for notification issues
+- `GITHUB_OWNER`: The owner of the notification repo
+- `GITHUB_REPO`: The repo name of the notification repo
+- `GITHUB_APP_ID`: The app ID of the notification GitHub app
+- `GITHUB_APP_PRIVATE_KEY`: The RSA private key for the notification GitHub app
 
 Build configuration: `DOES_IT_BUILD_OVERRIDE_VERSION` to override the git commit.
 
 ## Deployment
 
 deployed at <https://does-it-build.noratrieb.dev/>
+
+## Notification
+
+does-it-build supports sending target maintainer notifications on breakage.
+
+It does this by creating an issue <https://github.com/Noratrieb/does-it-build-notifications> that pings the registered maintainers.
+There is an array in the source code (linked to on the website target page) where people can add or remove themselves.