fix: Update documentation.

Author: goloroden

README.md

@@ -16,7 +16,7 @@ Install the client SDK:
 composer require thenativeweb/eventsourcingdb
 ```
 
-Import the package and create an instance by providing the URL of your EventSourcingDB instance and the API token to use:
+Import the `Client` class and create an instance by providing the URL of your EventSourcingDB instance and the API token to use:
 
 ```php
 require __DIR__ . '/vendor/autoload.php';
@@ -39,3 +39,54 @@ If you want to verify the API token, call `verifyApiToken`. If the token is inva
 ```php
 $client->verifyApiToken();
 ```
+
+### Using Testcontainers
+
+Import the `Container` class, call the `start` function to run a test container, get a client, run your test code, and finally call the `stop` function to stop the test container:
+
+```php
+require __DIR__ . '/vendor/autoload.php';
+
+use Thenativeweb\Eventsourcingdb\Container;
+
+$container = new Container();
+$container->start();
+
+$client = $container->getClient();
+
+// ...
+
+$container->stop();
+```
+
+To check if the test container is running, call the `isRunning` function:
+
+```php
+$isRunning = $container->isRunning();
+```
+
+#### Configuring the Container Instance
+
+By default, `Container` uses the `latest` tag of the official EventSourcingDB Docker image. To change that, call the `withImageTag` function:
+
+```php
+$container = new Container()
+  ->withImageTag("1.0.0");
+```
+
+Similarly, you can configure the port to use and the API token. Call the `withPort` or the `withApiToken` function respectively:
+
+```php
+$container = new Container()
+  ->withPort(4000)
+  ->withApiToken("secret");
+```
+
+#### Configuring the Client Manually
+
+In case you need to set up the client yourself, use the following functions to get details on the container:
+
+- `getHost()` returns the host name
+- `getMappedPort()` returns the port
+- `getBaseUrl()` returns the full URL of the container
+- `getApiToken()` returns the API token