- Use [document-features](https://crates.io/crates/document-features)
  crate to automatically add documentation about the features to the
  crate documentation at the crate level.
- Use the doc_auto_cfg feature to automatically add documentation
  to every item that requires a feature flag to be enabled. This is
  behind a docsrs feature flag as it can only be enabled using the
  nightly toolchain and this allows the documentation to be built with
  the stable toolchain when the feature is not enabled. See
  <https://doc.rust-lang.org/rustdoc/unstable-features.html#doc_auto_cfg-automatically-generate-doccfg>
  for more information.
- Automatically scrape example code into the documentation using the
  unstable rustdoc-scrape-examples feature. See
  <https://doc.rust-lang.org/nightly/rustdoc/scraped-examples.html> for
  more information.

To test this change, run:
```shell
RUSTDOCFLAGS="--cfg docsrs" \
  cargo +nightly doc \
    -Zunstable-options -Zrustdoc-scrape-examples \
    --all-features --no-deps --open
```