Add corresponding Ressources to each part and estimate how much time that takes to learn this

Add corresponding resources to each part and estimate how much time that takes to learn this from zero to hero.

For instance to learn kotlin :
  - https://hyperskill.org/tracks/18
  - https://kotlinlang.org/docs/home.html
  - https://developer.android.com/kotlin
  - https://www.udacity.com/course/kotlin-bootcamp-for-programmers--ud9011
