example: add font_sdf.zig

examples/text/resources/shaders/glsl100/alpha_discard.fs

@@ -0,0 +1,20 @@
+#version 100
+
+precision mediump float;
+
+// Input vertex attributes (from vertex shader)
+varying vec2 fragTexCoord;
+varying vec4 fragColor;
+
+// Input uniform values
+uniform sampler2D texture0;
+uniform vec4 colDiffuse;
+
+void main()
+{
+    vec4 texelColor = texture2D(texture0, fragTexCoord);
+
+    if (texelColor.a == 0.0) discard;
+
+    gl_FragColor = texelColor*fragColor*colDiffuse;
+}