refactor: exported modules from core should be mapped with their types

[louis-jan]

Problem
In PR #948, we encountered an issue where we could not import node modules exported by @janhq/core but were only able to require them since modules were not exported accordingly.

In this PR, we refactored to have three exported modules:

• @janhq/core: default UMD module root, serving as its core SDK, can be imported from both browsers and Node.
• @janhq/core/sdk: ES5 core SDK module, importable from browser projects.
• @janhq/core/node: CommonJS Node module, importable from Node projects.

Success Criteria
Refactored modules import

// from 
const node = require('@janhq/core/dist/node/index.cjs')
// to
import  { ... } from '@janhq/core/node'

Additional context
Include any other relevant context or screenshots about the feature request here.