Add automation to update Fastly IP list periodically

[egeakman]

• The workflow runs every Sunday at 00:00.
• It can also be run manually through Actions >> Update Fastly IP List (on the left panel) >> Run workflow.

The workflow normally pushes directly to the default branch, but we can configure it to push to another branch and then open a pull request. Also, we can change the file names and their locations if it doesn't fit this project's hierarchy.

Here is an example result: https://github.com/egeakman/psf-salt-test/commit/0842a11f3b236457d8d872bc01449c5d248da7c1 Example workflow run: https://github.com/egeakman/psf-salt-test/actions/runs/3832653799/jobs/6523216658

Closes #291

[egeakman]

CC: @ewdurbin, @cegerhardson

[egeakman]

Closing the pull request since the issue has been resolved. Although it would have been nice if someone had taken a look. By the way, I am still waiting for the d.p.o logs (https://github.com/python/python-docs-es/issues/2253#issuecomment-1383340956).