Create a developer 'Quickstart' page

[fhennig]

As a contributor with maybe some previous knowledge, I don't want to read lenghty instructions on how to get geoing. I want to read a quick page that is mostly shell script commands that I can run to get going.

The goal should be to have a dev environemnt where I can change things in the operator and test it in kind.

steps:

• show how to install the dependencies (apt install gzip kind kuttl ...)
  • Problem: Lot's of tools, a lot of them installable in a different way, annoying to maintain such a list
• configure git signing
• show how to make changes to an operator
  • git clone
  • make a change
  • run checks (cargo clippy --all-targets)
  • run ./scripts/test.sh
  • Raise PR

[fhennig]

Alternative idea: an ansible script or similar to set up a dev environment