Documentation addition

[joel1st]

Not sure if this is useful for anyone else, but this pattern works well when adding it to the project with existing developers using it.
Rather than asking people to run npm install for the first time, this will run npm install if install-changed is not found.

    "prestart": "install-changed || npm install",
    "start": "ts-node build_tools/develop.ts",

I have only tested this on linux, there may be different approaches required for windows.

Very handy package btw :)