Fixed path in example

[thchia]

I'm not sure if I'm missing something, but the import in index.tsx in the react example directory does not point to a valid location. It points to the package root, when I think it should point to either src/index.tsx or dist/index.tsx (but probably the former).

[Carl-Foster]

When the path points to the package root, it loads the package from the dist folder, as defined in package.json. This means that the example code runs the compiled components which is ideal for testing.
It's noted in the docs to run both the start command for tsdx and the example package separately to enable this.