Add release notes for another 2020 May backend release (#431)
Add release notes for another 2020 May backend release (#431)

* Add release notes for the next backend release

* Add May 2020 vol 2 release notes.

Co-authored-by: tusmester <d9584d3666b390628cb915eacbcee0e3f18a44b6@gmail.com>
SenseNet/sensenet.github.io,SenseNet/sensenet.github.io,SenseNet/sensenet.github.io