Splat Texture (#79)

* Add experimental Splat Texture rendering and examples/splat-texture. Added star.png and heart.png to assets.json and to assets repo. Update examples/depth-of-field to compute from metric aperture size. Added SparkRenderer.renderScale debug parameter. Updated examples/editor: set default highDPI to true, added logFocalDistance, apertureAngle, refactored, grouped into debugFolder, default settings open, preset buttons for nonAA and AA settings.

* Set default highDpi in examples/editor to not(isMobile).

examples/assets.json

@@ -102,5 +102,13 @@
   "valley.spz": {
     "url": "https://sparkjs.dev/assets/splats/valley.spz",
     "directory": "splats"
+  },
+  "star.png": {
+    "url": "https://sparkjs.dev/assets/images/star.png",
+    "directory": "images"
+  },
+  "heart.png": {
+    "url": "https://sparkjs.dev/assets/images/heart.png",
+    "directory": "images"
   }
 }