Make debezium-examples testable with CI/CD

I started a small PoC to find out how we could make updates to debezium-examples testable and easier + safer to update to newer versions by having CI/CD tests to validate changes and that examples still work.

https://github.com/debezium/debezium-examples/compare/master...rk3rn3r:make-examples-testable-poc

suggested process:

• migrate markdown documents to asciidoc (can be automated using pandoc), in order to extract example bash calls to scripts and then include script content in asciidoc
• either switch to asciidoc as default or use CI/CD to build markdown from asciidoc
• externalize all bash / test code calls to scripts and setup CI/CD automation to verify examples are working
• setup CI/CD pipeline to automatically test changes to debezium-examples
• make DEBEZIUM_VERSION a variable where it's hardcoded