a complete set of documentations for the repo and pkg

[zuhengxu]

[zuhengxu]

The docs are added in https://github.com/TuringLang/NormalizingFlows.jl/pull/27.

[zuhengxu]

@JuliaRegistrator register

[JuliaRegistrator]

Registration pull request created: JuliaRegistries/General/90238

After the above pull request is merged, it is recommended that a tag is created on this repository for the registered package version.

This will be done automatically if the Julia TagBot GitHub Action is installed, or can be done manually through the github interface, or via:

git tag -a v0.1.0 -m "<description of version>" 2f788758c43bf945d3ce4459b104f4d1038a4dc2
git push origin v0.1.0