[Doc] Creation of "how-to" documentation

[antonkri]

• Demo applications have exhaustive "how-to" documentation, that basically guide the user from the very beginning to the very end, explaining every step of the software development process

[nmohanan31]

Handbook has scrample tests to start with: https://eclipse-score.github.io/score/main/handbook/building_simple_application/reference_integration.html

cc: @FScholPer