add pyecore python package

[donvini94]

I packaged this python package and this is the first package I packed and try to contribute.

I wasn't really sure if I needed propagatedBuildInputs or buildInputs, both seem to work.

I tested with, but also unsure about how to go about this.

nix-build -A python3Packages.pyecore
nix-shell -I nixpkgs=. -p python3Packages.pyecore --run "python -c 'import pyecore'"

• Built on platform(s)

  • [ x] x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin

• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)

  • sandbox = relaxed
  • sandbox = true

• [x ] Fits CONTRIBUTING.md.