Create/Update assets for version 1.19-pre3

assets/minecraft/shaders/program/downscale.fsh

@@ -0,0 +1,19 @@
+#version 150
+
+uniform sampler2D DiffuseSampler;
+
+in vec2 texCoord;
+in vec2 oneTexel;
+
+uniform vec2 InSize;
+
+out vec4 fragColor;
+
+void main() {
+    vec3 Texel0 = texture(DiffuseSampler, texCoord).rgb;
+    vec3 Texel1 = texture(DiffuseSampler, texCoord + vec2(oneTexel.x, 0.0)).rgb;
+    vec3 Texel2 = texture(DiffuseSampler, texCoord + vec2(0.0, oneTexel.y)).rgb;
+    vec3 Texel3 = texture(DiffuseSampler, texCoord + oneTexel).rgb;
+
+    fragColor = vec4((Texel0 + Texel1 + Texel2 + Texel3) * 0.25, 1.0);
+}