MOVE/CONVERT [homerun-demo-stack] to updated helmfile format

[patrick-hermann-sva]

copy content (not all files or the whole folder..) from:
https://github.com/stuttgart-things/stuttgart-things/tree/main/helm/homerun-demo-stack

to the same format like the homerun-base-stack in this repo.

• helmfile must be abled to be rendered with default values
• test deploy (in combination with base-stack)
• test app
• update readme for deployment and test
• create pr + request review