Create/Update assets for version 1.21

assets/minecraft/shaders/core/position_tex.vsh

@@ -0,0 +1,15 @@
+#version 150
+
+in vec3 Position;
+in vec2 UV0;
+
+uniform mat4 ModelViewMat;
+uniform mat4 ProjMat;
+
+out vec2 texCoord0;
+
+void main() {
+    gl_Position = ProjMat * ModelViewMat * vec4(Position, 1.0);
+
+    texCoord0 = UV0;
+}