API and client - update notes

Ditto-client

Eclipse Ditto release notes

• ditto-client - 2.1.1 released 2021-10
• ditto-client - 2.1.0 released 2021-09
• ditto-client - 2.0.0 released 2021-05
• ditto-client - 1.5.1 released 2020-12
• ditto-client - 1.5 released 2020-12
• ditto-client - 1.4 released 2020-10
• ditto-client - 1.3 released 2020-09
• ditto-client - 1.2 released 2020-08
• ditto-client - 1.1 released 2020-04
• ditto-client - 1.0 released 2019-12