chore: add api lite readme

lib/matrix_api_lite/README.md

@@ -0,0 +1,45 @@
+# Matrix API Lite
+
+This package is a dead simple data model over the client-server specification of https://matrix.org and is mostly used as a base for a more complete Matrix SDK.
+It doesn't contain any logic and just provides methods for all API endpoints and json parser for all objects. It is intended to be as close to the specificaton
+as possible so we get a 1:1 relationship with the API. More complex logic like a sync loop or a data model for rooms should be implemented in a more complete
+Matrix SDK.
+
+## Usage
+
+A simple usage example:
+
+```dart
+import 'package:matrix/matrix_api_lite.dart';
+
+void main() async {
+  final api = MatrixApi(homeserver: Uri.parse('https://matrix.org'));
+  final capabilities = await api.requestServerCapabilities();
+  print(capabilities.toJson());
+}
+
+```
+
+## Generated code
+
+The files in `lib/src/generated` are generated by [dart_openapi_codegen](https://gitlab.com/famedly/company/frontend/dart_openapi_codegen/)
+from [matrix-spec](https://github.com/matrix-org/matrix-spec/).
+
+To regenerate the code, follow these steps:
+
+1. Clone both repositories next to each other
+  1.1 `git clone git@github.com:famedly/dart_openapi_codegen.git`
+  1.2 `git clone git@github.com:famedly/matrix-dart-sdk.git`
+2. Execute the script in the dart_openapi_codegen directory:
+```sh
+cd dart_openapi_codegen
+./scripts/matrix.sh ../matrix-dart-sdk/lib/matrix_api_lite/generated
+cd ..
+```
+3. Run the build_runner in the matrix_api_lite directory to generate enhanced_enum stuff:
+```sh
+cd matrix-dart-sdk
+dart pub get
+dart run build_runner build
+```
+4. Check lints and tests and create a merge request