Add automated testing for examples

It would be great is we could automate the testing of these examples. The Kafka tutorials micro-site is a good example of how this can be done.

Such automation would:
1. Ensure we know everything is working for the current / past releases
1. Give us early warnings / failures if an upcoming release brakes anything, (e.g. if we have a branch building of ksqlDB's master branches latest images
1. Speed up the task of updating the examples