Update migration instructions for 2.16.0

Closes wmonk/create-react-app-typescript#322

Author: sven3270350

Diff for: README.md

@@ -21,6 +21,10 @@ npm start
 
 In general, most upgrades won't require any migration steps to work, but if you experience problems after an upgrade, please file an issue, and we'll add it to the list of migration steps below.
 
+### From `<2.16.0` to `>=2.16.0`
+
+Since `2.16.0`, the template uses different `tsconfig` files for both development and production mode. For the latter, unfortunately, the path resolver is not smart enough to fall back to the basic `tsconfig.json` in case the expected `tsconfig.prod.json` is not present, so you have to create this file manually like shown [here](https://github.com/wmonk/create-react-app-typescript/blob/master/packages/react-scripts/template/tsconfig.prod.json).
+
 ### From `<2.13.0` to `>=2.13.0`
 
 Since `2.13.0`, `typescript` is listed as a peer dependency of `react-scripts-ts`. For projects generated with at least this version, the init script takes care of properly installing it as dev dependency to the generated projects. Older projects require manual installation, in case you have not already done that.