Add documentation

Author: AdrienVannson

docs/getting-started.md

@@ -10,7 +10,6 @@ You can also use it from `grpcio-tools`:
 pip install grpcio-tools
 ```
 
-
 ## Install `betterproto2_compiler`
 
 It is possible to install `betterproto2_compiler` using pip:
@@ -19,10 +18,6 @@ It is possible to install `betterproto2_compiler` using pip:
 pip install betterproto2_compiler
 ```
 
-!!! warning
-    The compiler needs Python 3.10, 3.11 or 3.12. Don't worry! The generated code will be compatible with all Python versions from Python 3.8 to Python 3.13.
-
-
 ## Compile a proto file
 
 Create the following `example.proto` file.
@@ -35,6 +30,10 @@ package helloworld;
 message HelloWorld {
     string message = 1;
 }
+
+service HelloService {
+    rpc SayHello (HelloWorld) returns (HelloWorld);
+}
 ```
 
 You should now be able to compile it using:
@@ -50,3 +49,40 @@ If you installed `protoc` with `grpc-tools`, the command will be:
 mkdir lib
 python -m grpc.tools.protoc -I . --python_betterproto2_out=lib example.proto
 ```
+
+### Service compilation
+
+#### Clients
+
+By default, for each service, betterproto will generate a synchronous client. Both synchronous and asynchronous clients
+are supported.
+
+  - Synchronous clients rely on the `grpcio` package. Make sure to enable the `grpcio` extra package when installing
+    betterproto2 to use them.
+  - Asynchronous clients rely on the `grpclib` package. Make sure to enable the `grpclib` extra package when installing
+    betterproto2 to use them.
+
+To choose which clients to generate, use the `client_generation` option of betterproto. It supports the following
+values:
+
+  - `none`: Clients are not generated.
+  - `sync`: Only synchronous clients are generated.
+  - `async`: Only asynchronous clients are generated.
+  - `sync_async`: Both synchronous and asynchronous clients are generated.
+        Asynchronous clients are generated with the Async suffix.
+  - `async_sync`: Both synchronous and asynchronous clients are generated.
+        Synchronous clients are generated with the Sync suffix.
+  - `sync_async_no_default`: Both synchronous and asynchronous clients are generated.
+        Synchronous clients are generated with the Sync suffix, and asynchronous clients are generated with the Async
+        suffix.
+
+For example, `protoc -I . --python_betterproto2_out=lib example.proto --python_betterproto2_opt=client_generation=async`
+will only generate asynchronous clients.
+
+#### Servers
+
+By default, betterproto will not generate server base classes. To enable them, set the `server_generation` option to
+`async` with `--python_betterproto2_opt=server_generation=async`.
+
+These base classes will be asynchronous and rely on `grpclib`. To use them, make sure to install `betterproto2` with the
+`grpclib` extra package.