Add conda env, Github Actions CI, and VS Code devcontainer

[nick-youngblut]

I've added a conda env, in which all of the dependency versions are specified, and I've added a bare-bones CI for testing that make works with the conda env.

[nick-youngblut]

Note: the VS Code devcontainer includes the Copilot extension, which you should be able to use for free, since you are an open source developer.

[zjshi]

Thanks Nick, I will note that you've added conda env in the main docs.