Change to src/package structure

[AdamRJensen]

The recommended package structure is to follow the src/package folder structure, see reasoning here and here.

This has been discussed for the pvlib-python package: pvlib/pvlib-python#2403

This change only requires a few modifications to the pyproject.toml file.

@echedey-ls, @kandersolar I think it makes sense to test it out on this package as it's much simpler and will give us an idea of what needs to be changed.

[AdamRJensen]

This change also required configuring the pyproject.toml file to recognize the package name space.

[tool.setuptools.packages.find]
where = ["src"]  # list of folders that contain the packages (["."] by default)

[echedey-ls]

I miss CI testing both sdist and bdist get built correctly too, may I open a PR for that?

[AdamRJensen]

I miss CI testing both sdist and bdist get built correctly too, may I open a PR for that?

@echedey-ls Please do! I'm trying to keep this repository up to date as a template on which to base new packages on.

In fact, as an editor for JOSS, I often refer people to this rather simple package for good practices.

[kandersolar]

I don't see any issues here. I built the distribution files locally and they looked fine. I suggest merging this and then verifying that #64 still works as expected.