A description about Apache Flink is missing

Write an article about how to use Apache Flink.

assigned to @s2817051--tu-dresden.de

mentioned in commit 2ca08ea8

mentioned in merge request !409 (merged)

mentioned in commit e98e423c

closed with commit 2ca08ea8

closed with merge request !409 (merged)

mentioned in merge request !439 (merged)

mentioned in commit a1ba4d02