Add javactrl-kafka

[awto]

This is my tool displaying how stateful stream processors can be used for defining workflows as code. Basically, this is more of an approach rather than a tool, the tool is very minimalistic but depends on my delimited continuations implementation. Though just after Java (or Kotlin) gets its own persistent continuations the approach will work without any library.

[manuzhang]

Please add your language tag like [java]

[awto]

Added