[FLINK-20598] [training] Update playgrounds for Flink 1.12 (#21)
-rw-r--r-- 68 .gitignore
-rw-r--r-- 11357 LICENSE
-rw-r--r-- 2341 README.md
drwxr-xr-x - docker
-rw-r--r-- 4881 howto-update-playgrounds.md
drwxr-xr-x - operations-playground
drwxr-xr-x - pyflink-walkthrough
drwxr-xr-x - table-walkthrough