Error when targeting ES2015+

Hi,

I'm currently trying to build a simple app with Dojo 2 and used the `dojo-cli` to create a project. I noticed in the generated `tsconfig.json` that the target is set to `es5`. With this setting my application is working fine, however if I try to set the target to ES2015+, I get a run-time error.

To reproduce this issue, just create a project with `dojo-cli` and change the target in `tsconfig.json` to `es2015`.

So now I'm wondering why a brand new framework like Dojo 2 can't be compiled to ES2015+...