🔧 Pass window padding to the shaders

docs/how-to-create-new-effects.md

@@ -92,6 +92,7 @@ Please study this code carefully, all of it is explained with inline comments.
 // float     uProgress:   A value which transitions from 0 to 1 during the entire animation.
 // float     uTime:       A steadily increasing value in seconds.
 // vec2      uSize:       The size of uTexture in pixels.
+// float     uPadding:    The empty area around the actual window (e.g. where the shadow is drawn).
 #include "common/uniforms.glsl"
 
 // The width of the fading effect is loaded from the settings.