Update tsconfig to support dynamic import

[nicolaserny]

resolves #90

In order to make code splitting work, we have to set the module to esnext in tsconfig.json

[nicolaserny]

@wmonk using esnext seems to have an impact on tests (SyntaxError: Unexpected token import).
The weird part is that tests (yarn test) work on my projects created with create react app ts + changing module to esnext.
I'm not sure it's a good idea to override the tsconfig file used by jest...

[nicolaserny]

@wmonk only a temporary fix (for jest) because TS_CONFIG is deprecated
https://github.com/kulshekhar/ts-jest
as we provide a tsConfigFile value, the module is not overwritten to commonjs...

[DorianGrey]

What about creating a tsconfig.test.json which uses the extends directive and overrides the module field along with the regular tsconfig.json, and update the reference to tsConfigFile accordingly? Path may be added like the current one that references the regular tsconfig.json.

I.e.:
tsconfig.test.json

{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "module": "commonjs"
  }
}

Add corresponding path entries in this file, e.g. appTsTestConfig (keep in mind that there are multiple positions to be extended, i.e. L84 and L114.
As a last step, change the variable here to your new one.

It's a bit tricky, but different module values are required under different circumstances:

• esnext for the dynamic import call
• commonjs to get things working on node.js

Using different config files for both situations should be the way to go here.

[DorianGrey]

@wmonk:
Change looks good technically. Your turn now :)

[wmonk]

Thanks!