docs: add docs and examples (#2127)

examples/input-pointerButton.ts

@@ -0,0 +1,71 @@
+/**
+ * @title input-pointerButton
+ * @category input
+ * @thumbnail https://mdn.alipayobjects.com/merchant_appfe/afts/img/A*ytliRpOHgvgAAAAAAAAAAAAADiR2AQ/original
+ */
+import {
+  Camera,
+  DirectLight,
+  MeshRenderer,
+  PBRMaterial,
+  PointerButton,
+  PrimitiveMesh,
+  Script,
+  TextRenderer,
+  Vector3,
+  WebGLEngine,
+} from "@galacean/engine";
+import { LitePhysics } from "@galacean/engine-physics-lite";
+
+// Create engine
+WebGLEngine.create({ canvas: "canvas", physics: new LitePhysics() }).then(
+  (engine) => {
+    engine.canvas.resizeByClientSize();
+    const scene = engine.sceneManager.activeScene;
+    const rootEntity = scene.createRootEntity("root");
+
+    // add light
+    const lightEntity = rootEntity.createChild("light");
+    lightEntity.addComponent(DirectLight);
+    lightEntity.transform.setRotation(-45, 0, 0);
+
+    // init camera
+    const cameraEntity = rootEntity.createChild("camera");
+    cameraEntity.addComponent(Camera);
+    cameraEntity.transform.setPosition(10, 10, 10);
+    cameraEntity.transform.lookAt(new Vector3(0, 0, 0));
+
+    // init box
+    const boxEntity = rootEntity.createChild("box");
+    const renderer = boxEntity.addComponent(MeshRenderer);
+    renderer.mesh = PrimitiveMesh.createCuboid(engine, 1, 1, 1);
+    renderer.setMaterial(new PBRMaterial(engine));
+    boxEntity.addComponent(RotateScript);
+
+    // add tip
+    const textEntity = rootEntity.createChild("text");
+    textEntity.transform.rotationQuaternion =
+      cameraEntity.transform.rotationQuaternion;
+    textEntity.transform.setPosition(0, 5, 0);
+    textEntity.transform.setScale(2, 2, 2);
+    const textRenderer = textEntity.addComponent(TextRenderer);
+    textRenderer.fontSize = 40;
+    textRenderer.text =
+      "Hold down the 'Primary'  to rotate left\nHold down the 'Secondary' to rotate right\n";
+
+    // Run engine
+    engine.run();
+  }
+);
+
+class RotateScript extends Script {
+  onUpdate(deltaTime: number): void {
+    const { engine, entity } = this;
+    if (engine.inputManager.isPointerHeldDown(PointerButton.Primary)) {
+      entity.transform.rotate(0, -1, 0);
+    }
+    if (engine.inputManager.isPointerHeldDown(PointerButton.Secondary)) {
+      entity.transform.rotate(0, 1, 0);
+    }
+  }
+}