gpu: [compute] pre-transform images before rendering

We're about to change the last stage of the compute pipeline to only
accept images, not sampled textures. This change prepares materials
for pixel-aligned image copying by pre-rendering images to a texture,
applying transforms.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/shaders/material.vert

@@ -0,0 +1,15 @@
+#version 310 es
+
+// SPDX-License-Identifier: Unlicense OR MIT
+
+precision highp float;
+
+layout(location = 0) in vec2 pos;
+layout(location = 1) in vec2 uv;
+
+layout(location = 0) out vec2 vUV;
+
+void main() {
+	vUV = uv;
+	gl_Position = vec4(pos, 0, 1);
+}