Update the Readme

Signed-off-by: Jonathan Schwender <[email protected]>

Readme.md

@@ -1,13 +1,33 @@
 # ohos-sys
 
-FFI-bindings for the native API of OpenHarmony OS.
+FFI-bindings for the native API of OpenHarmony OS. See the [documentation] for a list of supported components.
 This crate is under active development, and not officially affiliated with OpenHarmony OS.
 
 ## Development
 
-The current bindings are generated with `bindgen` using `scripts/generate_bindings.sh` with version
-`4.0.10.13` of the OpenHarmony SDK.
+The current bindings are generated with `bindgen` using `scripts/generate_bindings.sh`.
+A separate file is generated for each API version, and (assuming no breaking changes) the new additions are
+manually copied to an `apiXX_additions.rs` file, which is included as a module if `feature = api-XX` is selected.
+The generated file `drawing_apiXX.rs` should be committed to version control, so we can easily rerun the script on a 
+patch-release for a given API-level and see what changed.
+The file itself is however not needed, and will be excluded from `crates.io` releases.
+
+# Contributing
+
+There are still quite a few OpenHarmony APIs missing. Feel free to contribute missing APIs, but be sure to adapt
+the script, so your bindings are reproducible! 
+Please also check the following:
+
+- Ensure that opaque struct definitions do not derive `Copy`, `Clone` and `Debug`.
+- Blocklist all unnecessary type definitions, e.g. from the C standard library.
+- Preferably generate the bindings with libclang in `C` mode. However, if a header file is not C-compliant
+  due to an issue of the OpenHarmony SDK, then setting `libclang` to C++ mode is fine.
+- Be sure to guard the new component behind a cargo feature and document the feature in Cargo.toml.
+- If you did not generate the bindings with API-level 10, specify which API-level you generated the bindings with
+  and guard the generated module behind the corresponding api-level feature flag.
 
 ## License
 
 This crate is licensed under the Apache-2.0 license, matching the OpenHarmony OS SDK.
+
+[documentation]: https://docs.rs/ohos-sys/latest/ohos_sys/