docs(viewport): add viewport-module documentation

Author: Valentin Vetter

playground/extensions/extensions-6-viewport.md

@@ -0,0 +1,47 @@
+# ViewportModule
+
+This module allows you to create a viewport where you can zoom with mousewheel, and click/drag to move.
+
+## Import
+
+⚠ This module requires the [GraphicEntityModule](https://github.com/CodinGame/codingame-game-engine/tree/master/engine/modules/entities) to work.
+
+Add this dependency in the `pom.xml` of your project:
+
+```xml
+<dependency>
+  <groupId>com.codingame.gameengine</groupId>
+  <artifactId>module-viewport</artifactId>
+  <version>3.7.0</version>
+</dependency>
+```
+
+And load the module in your `config.js`:
+
+```javascript
+import { GraphicEntityModule } from './entity-module/GraphicEntityModule.js';
+import { ViewportModule } from './viewport-module/ViewportModule.js';
+
+export const modules = [
+  GraphicEntityModule,
+  ViewportModule
+];
+```
+
+## Usage
+
+In your `Referee.java`:
+
+```java
+@Inject private GraphicEntityModule gem;
+@Inject ViewportModule viewportModule;
+
+@Override
+public void init() {
+  Group group = gem.createGroup();
+
+  // group.add(your entities)
+
+  viewportModule.createViewport(group);
+}
+```

techio.yml

@@ -49,6 +49,8 @@ plan:
     statement: playground/extensions/extensions-toggle.md
   - title: Anim Module
     statement: playground/extensions/extensions-5-animmodule.md
+  - title: Viewport Module
+    statement: playground/extensions/extensions-6-viewport.md
   - title: Create your own modules
     statement: playground/extensions/extensions-2-tutorial.md
 - title: One more thing