Implement ES6 module

[StefansArya]

Because this framework almost reach it's stable version and some fast build tools like snowpack/esbuild have showed up. I think it's the right time to implement ES6 module for this framework.

Feel free to contribute if you interested 😄

[StefansArya]

The ES6 module was implemented, but we still need to make it more efficient for the tree shaking.

[StefansArya]

Currently some module has circular dependency for:

- sf-model.js
- sf-component.js
- sf-space.js
- sf-model/*.js

I don't see any issues because of it and the circular dependency was expected.
But it may be fixed on the future.

If you want to remove the warning please add this config on your rollup.config.js:

export default {
  onwarn(warning, warn) {
    if (warning.code === 'CIRCULAR_DEPENDENCY') return;
    warn(warning);
  }
}