Show last successful build

[bhipple]

When all builds are failing, it would be nice to show the time of the last successful build. Example:

$ hydra-check topydo
Build Status for nixpkgs.topydo.x86_64-linux on unstable
✖ (Failed) topydo-0.13 from 2020-04-28 - https://hydra.nixos.org/build/117837434

Last Builds:
✖ (Failed) topydo-0.13 from 2020-04-23 - https://hydra.nixos.org/build/117370448
✖ (Failed) topydo-0.13 from 2020-04-19 - https://hydra.nixos.org/build/116905954
✖ (Failed) topydo-0.13 from 2020-04-05 - https://hydra.nixos.org/build/116125014
✖ (Failed) topydo-0.13 from 2020-04-02 - https://hydra.nixos.org/build/115754788
✖ (Failed) topydo-0.13 from 2020-03-27 - https://hydra.nixos.org/build/115542554
✖ (Failed) topydo-0.13 from 2020-03-24 - https://hydra.nixos.org/build/115470065
✖ (Failed) topydo-0.13 from 2020-03-16 - https://hydra.nixos.org/build/114750985
✖ (Failed) topydo-0.13 from 2020-03-08 - https://hydra.nixos.org/build/114102922
✖ (Failed) topydo-0.13 from 2020-03-04 - https://hydra.nixos.org/build/113823833

Hydra knows and displays the last successful build in this case:
https://hydra.nixos.org/build/117837434

In particular, this information is nice to have when looking at build failures in nixpkgs-review and determining whether it might be time to set meta.broken = true on the package (or look for a new version that might fix it).

[makefu]

I like the idea, however it seems there is no api endpoint we could trigger for and we must reside to parsing the html (again).

[makefu]

Hi @bhipple sorry for not showing more love to hydra-check, i just want to let you know i still think the issue is worth solving, however i currently do not have much time left to implement it.
If you would be willing to create a Pull Request i'd love to test and approve it!