Add WebGL compatibility

src/graphics/rendering/shaders/distance-fs-100.glsl

@@ -0,0 +1,23 @@
+#version 100
+
+precision lowp float;
+
+#define SURFACE_OFFSET 0.001
+ 
+uniform float maxMinDistance;
+uniform float distanceNdcPixelSize;
+varying vec2 position;
+
+{macroDefinitions}
+
+{declarations}
+
+void main() {
+    float minDistance = maxMinDistance;
+    float color = 0.0;
+
+    {functionCalls}
+
+    // minDistance / 2.0: NDC to UV scale
+    gl_FragColor = vec4(minDistance / 2.0, color, 0.0, 0.0);
+}