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.

templates/target.html

@@ -31,6 +31,18 @@
       older targets (older than November 2024) this does not always work
       reliably, so some failed std builds there are simply no-std targets.
     </p>
+    <p>
+      🔔 does-it-build supports sending notifications to target maintainers via GitHub issues.
+      You can add yourself with <a href="{{notification_pr_url}}">a PR</a>.
+    </p>
+    {% if let Some(maintainers) = maintainers %}
+    <p>
+      Maintainers that will receive pings for this target:
+      {% for maintainer in maintainers %}
+      <a href="https://github.com/{{maintainer}}">{{maintainer}}</a>
+      {% endfor %}
+    </p>
+    {% endif %}
     {% if showing_failures %}
     <p>
       <a href="/target?target={{target}}">show all</a>