MNT: Add GHA schedule

[GuillaumeFavelier]

This PR adds a schedule for the GitHub Actions CIs. This will help to relieve the pain of #76 for example. By failing early, it draws attention on maintenance at least. What do you think @pyvista/developers ?

[codecov]

Codecov Report

Merging #83 (23c5aa8) into master (b1faea7) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #83   +/-   ##
=======================================
  Coverage   98.36%   98.36%           
=======================================
  Files           7        7           
  Lines         612      612           
=======================================
  Hits          602      602           
  Misses         10       10           

[akaszynski]

That's a great idea. I recently ran into an issue when building one of my other builds that ran into an issue due to a numpy version change. It's a good idea to implement daily builds and I think this would be useful for pyvista as well. In fact, we need to move over some of our builds to github CI so we can reduce the time it takes to run CI by splitting up the tests between GitHub Actions and Azure Pipelines.

[GuillaumeFavelier]

In fact, we need to move over some of our builds to github CI

I'll be glad to help on this 👍

[akaszynski]

That would great!

I'm thinking of moving the doc build over since we can upload the artifacts of each doc-build. Plus, there are github actions to upload docs to gh-pages (like github-pages-deploy-action). See https://github.com/pyansys/pymapdl/blob/master/.github/workflows/ci-build.yml