Add compilerOptions.rootDir=src setting to tsconfig.json
Add compilerOptions.rootDir=src setting to tsconfig.json

This is required for the recent demo of cross-repo linking to mobx
See https://twitter.com/mweststrate/status/1074609242521436160

mweststrate/MOBservable,mweststrate/MOBservable,mobxjs/mobx,mobxjs/mobx,mobxjs/mobx,mweststrate/MOBservable,mobxjs/mobx