CI building main

[rakeden]

Is your feature request related to a problem? Please describe. We want to make sure, that the site is being built by gh-pages

Describe the solution you'd like Add CI through github actions. Require CI in PRs to be run before merging.

Describe alternatives you've considered none.

Additional context

• run with local config
• build site with custom theme

[rakeden]

3dkrender has done that. good job!