Keep environment.ts a separate file when bundling for browser

[mensch72]

When doing ionic build --prod, the file environment.ts (after being replaced by environment.prod.ts) gets minimized, uglified and bundled.

We should prevent this (if possible), so that environment.ts remains a separate, non-uglified file in the browser bundle.

(We still want the rest of the code to be optimized for production of course)

Rationale: We’d like to distribute the pre-built bundle to different server admins for installation on their servers, and they need to make local adjustments to environment.ts. I want to spare them the effort to do a local build only because they need to adjust one value in environment.ts.

Related Ionic forum question: https://forum.ionicframework.com/t/keep-environment-ts-a-separate-file-in-bundling-for-browser/228731