WIP: docs: Document feature flags

Open question:
- What is the function of `prost-derive` feature?

README.md

@@ -463,6 +463,10 @@ The prost project maintains flakes support for local development. Once you have
 nix and nix flakes setup you can just run `nix develop` to get a shell
 configured with the required dependencies to compile the whole project.
 
+## Feature Flags
+- `std`: Enable integration with standard library. Disable this feature for `no_std` support. This feature is enabled by default.
+- `prost-derive`: TODO: That does this do? This feature is enabled by default.
+- `no-recursion-limit`: Disable the recursion limit. The recursion limit is 100 and cannot be customized. 
 
 ## FAQ
 

prost-build/src/lib.rs

@@ -124,6 +124,10 @@
 //!
 //! // Now compile your proto files via prost-build
 //! ```
+//! 
+//! ## Feature Flags
+//! - `format`: Format the generated output. This feature is enabled by default.
+//! - `cleanup-markdown`: Clean up Markdown in protobuf docs.
 //!
 //! [`protobuf-src`]: https://docs.rs/protobuf-src
 

prost-types/src/lib.rs

@@ -6,6 +6,9 @@
 //! definitions, so code examples are not in Rust.
 //!
 //! See the [Protobuf reference][1] for more information about well-known types.
+//! 
+//! ## Feature Flags
+//! - `std`: Enable integration with standard library. Disable this feature for `no_std` support. This feature is enabled by default.
 //!
 //! [1]: https://developers.google.com/protocol-buffers/docs/reference/google.protobuf