message: fix canvas painter not included in build
diff: export * from './lib/zrender';
  export * from './lib/export';
  -import './lib/svg/svg';
  +import {registerPainter} from './lib/zrender';
  +import CanvasPainter from './lib/canvas/Painter';
  +import SVGPainter from './lib/svg/Painter';
  +registerPainter('canvas', CanvasPainter);
  +registerPainter('svg', SVGPainter);
  \ No newline at end of file
  