Copy shaders from WR repo.

resources/shaders/ps_text.vs.glsl

@@ -0,0 +1,26 @@
+#line 1
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+struct Glyph {
+    PrimitiveInfo info;
+    vec4 color;
+    vec4 st_rect;
+};
+
+layout(std140) uniform Items {
+    Glyph glyphs[WR_MAX_PRIM_ITEMS];
+};
+
+void main(void) {
+    Glyph glyph = glyphs[gl_InstanceID];
+    VertexInfo vi = write_vertex(glyph.info);
+
+    vec2 f = (vi.local_clamped_pos - vi.local_rect.p0) / (vi.local_rect.p1 - vi.local_rect.p0);
+
+    vColor = glyph.color;
+    vUv = mix(glyph.st_rect.xy,
+              glyph.st_rect.zw,
+              f);
+}