enhance readme to provide better guidance for contributors

[olierxleben]

Problem I am facing:
When diving into this project the only help that is given is by showing how to build and setup for local development. This works great but any kind of new addition to the project seem to need manual steps which may not be clear, intuitively. That is the case especially when developing for this the first time.

Solution:
Writing detailed instructions of how to add a a dummy component and setup up all parts in the demo application to start developing for it.

Benefits:

• Less detail questions about development
• more contributions