fix(react): Add support for React Router sub-routes from handle

[onurtemizkan]

Adds support for lazy loading sub-routes / components using the pattern below:

const routes [
  // ...
  {
    path: 'part1',
      handle: {
        lazyChildren: () =>
          import('./pages/SomeMoreNestedRoutes').then(
        (mod) => mod.someMoreNestedRoutes
      ),
    },
  },
]