Fix web shaders

Got broken in https://github.com/emilk/egui/pull/187

egui_web/src/shader/fragment_100es.glsl

@@ -1,5 +1,3 @@
-#version 100 es
-
 precision mediump float;
 uniform sampler2D u_sampler;
 varying vec4 v_rgba;
@@ -13,6 +11,7 @@ vec3 srgb_from_linear(vec3 rgb) {
   return mix(higher, lower, vec3(cutoff));
 }
 
+// 0-255 sRGB  from  0-1 linear
 vec4 srgba_from_linear(vec4 rgba) {
   return vec4(srgb_from_linear(rgba.rgb), 255.0 * rgba.a);
 }
@@ -25,6 +24,7 @@ vec3 linear_from_srgb(vec3 srgb) {
   return mix(higher, lower, vec3(cutoff));
 }
 
+// 0-1 linear  from  0-255 sRGBA
 vec4 linear_from_srgba(vec4 srgba) {
   return vec4(linear_from_srgb(srgba.rgb), srgba.a / 255.0);
 }

egui_web/src/shader/fragment_300es.glsl

@@ -1,5 +1,3 @@
-#version 300 es
-
 precision mediump float;
 uniform sampler2D u_sampler;
 varying vec4 v_rgba;
@@ -13,6 +11,7 @@ vec3 srgb_from_linear(vec3 rgb) {
   return mix(higher, lower, vec3(cutoff));
 }
 
+// 0-255 sRGBA  from  0-1 linear
 vec4 srgba_from_linear(vec4 rgba) {
   return vec4(srgb_from_linear(rgba.rgb), 255.0 * rgba.a);
 }

egui_web/src/shader/vertex_100es.glsl

@@ -1,5 +1,3 @@
-#version 100 es
-
 precision mediump float;
 uniform vec2 u_screen_size;
 attribute vec2 a_pos;
@@ -16,6 +14,7 @@ vec3 linear_from_srgb(vec3 srgb) {
   return mix(higher, lower, vec3(cutoff));
 }
 
+// 0-1 linear  from  0-255 sRGBA
 vec4 linear_from_srgba(vec4 srgba) {
   return vec4(linear_from_srgb(srgba.rgb), srgba.a / 255.0);
 }

egui_web/src/shader/vertex_300es.glsl

@@ -1,5 +1,3 @@
-#version 300 es
-
 precision mediump float;
 uniform vec2 u_screen_size;
 attribute vec2 a_pos;
@@ -16,6 +14,7 @@ vec3 linear_from_srgb(vec3 srgb) {
   return mix(higher, lower, vec3(cutoff));
 }
 
+// 0-1 linear  from  0-255 sRGBA
 vec4 linear_from_srgba(vec4 srgba) {
   return vec4(linear_from_srgb(srgba.rgb), srgba.a / 255.0);
 }