[Migrating] Put in incremental compilation in tsconfig.json example

[pjonsson]

What cheatsheet is this about? (if applicable)

Migrating cheatsheet

What's your issue or idea?

The migration cheatsheet links the official guide for migrating from JS, but the example at https://www.typescriptlang.org/docs/handbook/migrating-from-javascript.html#writing-a-configuration-file does not contain "incremental": true.

I don't know how incremental compilation interacts with an IDE, but it saves a great deal of time when running tsc from the command line.