add PiP example

examples/pip.json5

@@ -0,0 +1,15 @@
+{
+  outPath: './pip.mp4',
+  width: 1280, height: 720, fps: 30,
+  enableFfmpegLog: true,
+  defaults: {
+    layer: { fontPath: './assets/Patua_One/PatuaOne-Regular.ttf' },
+  },
+  clips: [
+    { duration: 4, layers: [
+      { type: 'rainbow-colors' },
+      { type: 'video', path: './assets/tungestolen.mp4', resizeMode: 'contain', width: 0.4, height: 0.4, top: 0.05, left: 0.95, originY: 'top', originX: 'right' },
+      { type: 'title', position: 'bottom', text: 'Picture-in-Picture' }
+    ] },
+  ],
+}