message: get EXT_float_blend together with EXT_color_buffer_float
  firfox warns to do that for best support
diff: @@ -135,10 +135,12 @@ export interface COMPAT_color_buffer_float {
  export function getColorBufferFloat(gl: GLRenderingContext): COMPAT_color_buffer_float | null {
  if (isWebGL2(gl)) {
  if (gl.getExtension('EXT_color_buffer_float') === null) return null;
  + gl.getExtension('EXT_float_blend');
  return { RGBA32F: gl.RGBA32F };
  } else {
  const ext = gl.getExtension('WEBGL_color_buffer_float');
  if (ext === null) return null;
  + gl.getExtension('EXT_float_blend');
  return { RGBA32F: ext.RGBA32F_EXT };
  }
  }
  