Create/Update assets for version 1.16-pre3

assets/minecraft/shaders/program/screenquad.vsh

@@ -0,0 +1,14 @@
+#version 110
+
+attribute vec4 Position;
+
+uniform mat4 ProjMat;
+uniform vec2 OutSize;
+
+varying vec2 texCoord;
+
+void main() {
+    vec4 outPos = ProjMat * vec4(Position.xy, 0.0, 1.0);
+    gl_Position = vec4(outPos.xy, 0.2, 1.0);
+    texCoord = Position.xy / OutSize;
+}