Swagger UI debug embed (#534)

Add explanation of Swagger UI not being embedded on debug builds

---------

Co-authored-by: Daniél Kerkmann <daniel@kerkmann.dev>

README.md

@@ -282,6 +282,19 @@ This would produce api doc something similar to:
 - More about OpenAPI security in [security documentation](https://docs.rs/utoipa/latest/utoipa/openapi/security/index.html).
 - Dump generated API doc to file at build time. See [issue 214 comment](https://github.com/juhaku/utoipa/issues/214#issuecomment-1179589373).
 
+## General Pitfalls
+
+#### Swagger UI returns 404 Not Found from build binary
+
+This is highly probably due to `RustEmbed` not embedding the Swagger UI to the executable. This is natural since the `RustEmbed` 
+library **does not** by default embed files on debug builds. To fix this you can do one of the following.
+
+1. Build your executable in `--release` mode
+2. or add `debug-embed` feature flag to your `Cargo.toml` for `utoipa-swagger-ui`. This will enable the debug emebed feature flag for
+   `RustEmbed` as well. Read more about this [here](https://github.com/juhaku/utoipa/issues/527#issuecomment-1474219098) and [here](https://github.com/juhaku/utoipa/issues/268).
+
+Find `utoipa-swagger-ui` [feature flags here](https://github.com/juhaku/utoipa/tree/master/utoipa-swagger-ui#crate-features).
+
 # License
 
 Licensed under either of [Apache 2.0](LICENSE-APACHE) or [MIT](LICENSE-MIT) license at your option.