Badge request: F-Droid build status

:clipboard: **Description**

I would like to display the build status of the F-Droid app as a badge.

:link: **Data**
https://f-droid.org/repo/status/build.json
from https://forum.f-droid.org/t/possible-to-get-email-notification-for-build-failures/8905/2

:microphone: **Motivation**
This is because I would like to know if the build succeeds or not. It would be nice to have this simple way!

Start with the F-Droid build.json endpoint named in the issue and review the repository’s existing badge conventions for external status data. Done means a badge can display whether the F-Droid app build succeeds, with its behavior checked against the service’s available status data.

Written by the indexing model from the issue text.