Update to automatic github action build after upstream merge

[stes]

Once DeepLabCut/DeepLabCut#1777 is merged and published on PyPI, a GitHub action should be added for an automatic page build of https://benchmark.deeplabcut.org/. The steps to add are:

• Install latest version of DeepLabCut via pypi (or possibly use the suitable docker image?)
• Fetch the non-public ground truth dataset using a suitable github secrete (then not visible to the public, as intended)
• Run the tests to ensure that no upstream errors were introduced
• Run make deploy which will evaluate the benchmark results, and update the website table
• Update the page if all completed successfully

[MMathisLab]

@stes can we also automatically update website based on what is on main?