PiT: improve documentation

[manolo]

Quakus article should have:

• Section Adding dependencies should say that it does not apply when your project is already based on the quarkus starter project
• Section Vaadin Add-Ons should explain what the <name> part in the property means
• A section for packaging and running from production should be added as indicated in the README.md file
  • mvn package -Pproduction
  • java -jar target/quarkus-app/quarkus-run.jar