Add lightweight 2D WebGL cloud renderer as alternative to Vanta

config.js

@@ -6,6 +6,10 @@
  *               below. To add a new theme, drop a new *.css file in the same
  *               directory and add an entry to window.THEMES.
  *
+ * renderer    - Background renderer: 'vanta' (default, GPU 3D volumetric
+ *               clouds, heavy) or 'clouds2d' (lightweight 2D WebGL shader,
+ *               very low GPU usage, similar visual style).
+ *
  * units       - Measurement units for the weather widget.
  *               'metric' (°C, km/h) or 'imperial' (°F, mph)
  *
@@ -72,6 +76,7 @@ window.CONFIG = {
     debug: 0,
     theme: 'ash',
     units: 'metric',
+    renderer: 'clouds2d',  // 'vanta' or 'clouds2d'
     language: 'de',
     timeFormat: 'DD. MMMM, YYYY ‒ HH:mm:SS',
     location: {