Add early fail for `get_normal_newell` when the provided polygon is too small (< 3)

[mdjong1]

Fixes #176

[mdjong1]

Looks like the build failed trying to install/build cjvalpy 0.3.2. Maybe using latest cjvalpy would already resolve this?

#16 0.633 💥 maturin failed
#16 0.633   Caused by: The following metadata fields in `package.metadata.maturin` section of Cargo.toml are removed since maturin 0.14.0: classifier, requires-dist, requires-python, please set them in pyproject.toml as PEP 621 specifies.

[mdjong1]

Updating cjvalpy in the Dockerfile to 0.4.1 seems to have worked, I hope you're alright with that change :+1: