Fixed pip installation for submodules

[Nishit-Dua]

Issue

Installing from git+https://github.com/braun-steven/simple-einet doesn't install the submodules "layers" and "layers.distribution" wouldn't add simple_einet.layers to the environment, upon checking the setup for package, it wasn't included in the setup file hence the sub-directories weren't bundled with the main package.

Solution

Add the submodules to the package list, if it was a .py file using setuptools we could also use setuptools.find_packages(), but for toml I believe we need to list all sub-modules to be in pip installable package

Changes

Included "simple_einet.layers", "simple_einet.layers.distributions" in the list of modules to be packaged

[braun-steven]

Thank you for catching this 👍