Constant webxr::glwindow::PASSTHROUGH_VERTEX_SHADER

const PASSTHROUGH_VERTEX_SHADER: &[u8] = b"
  #version 330 core
  layout(location=0) in vec2 coord;
  out vec2 vTexCoord;
  void main(void) {
    gl_Position = vec4(coord, 0.0, 1.0);
    vTexCoord = coord * 0.5 + 0.5;
  }
";