Use default rollup polkadot.js config instead of webpack

[poka-IT]

Why do you use webpack instead of the default rollup conf existing for polkadot.js ?

https://github.com/polkadot-js/api/blob/master/rollup.config.mjs

Is there a technical reason ?

Rollup greatly minimizes the size of the build file since it selects only what is needed.
We thus go from 3.2MB currently generated by your webpack config to a few hundred KB

[RomeroYang]

cool, I will look into that.

[RomeroYang]

The js_api in sdk need to be backward compatible with some lower version webview for android devices. I tried rollup but the output can not run on my device for it has some advanced syntax.

Maybe you can try to see if you can come up with a working rollup config for this.