Add project documentation and generation instructions

This commit introduces the following:

- Generated Rust documentation.
- Updated `Cargo.toml` to use `rustls` as the TLS backend for HTTP client crates (`reqwest`, `rusoto_core`, `rusoto_route53`). This removes the dependency on OpenSSL and resolves potential build issues.
- Added a "Generating Documentation" section to `README.md` with instructions on how to generate and view the project documentation.

Author: google-labs-jules[bot]