Show all features in documentation using docsrs

[Wollac]

fixes #64

This will show all Modules, Traits, ... that are behind feature flags and add a "Available on crate feature host only." label on https://docs.rs.

Since cargo doc is also run in the CI, we might want to update this to a (nightly) version that also supports the --cfg docsrs flag, e.g.

      - uses: dtolnay/rust-toolchain@nightly
      - run: cargo doc --workspace --all-features --no-deps
        env:
          RUSTDOCFLAGS: "--cfg docsrs -D warnings"

[nategraf]

Need to update cargo doc in CI to use nightly

[nategraf]

I've added a docs.rs job which installs the nightly toolchain and does not install cargo-risczero or Foundry.
77a8c66