Merge pull request ComputationalRadiationPhysics#884 from ax3l/doc-addMaintainerBenj

Readme: Maintainer Updates

Author: psychocoderHPC

README.md

@@ -112,6 +112,9 @@ codes. See the [user guide](https://github.com/ComputationalRadiationPhysics/pic
 our [getting started video](http://www.youtube.com/watch?v=7ybsD8G4Rsk) and
 [contact](http://www.hzdr.de/db/Cms?pNid=132&pOid=30354) us!
 
+Please sign up on our **PIConGPU-Users** mailing list:
+[Subscribe (Feed)](https://cg.hzdr.de/Lists/picongpu-users/List.html)
+
 **Upgrades:** Every time we update the *master* branch, we publish a new release
 of PIConGPU. Before you pull the changes in, please read our [ChangeLog](CHANGELOG.md)!
 You may have to update some of your simulation `.param` files by hand
@@ -141,11 +144,9 @@ Active Team
 - Axel Huebl*
 - Maximilian Knespel
 - Richard Pausch*
-- Felix Schmitt*
-- Conrad Schumann
 - Stefan Tietze
 - Rene Widera*
-- Benjamin Worpitz
+- Benjamin Worpitz*
 
 ### Participants, Former Members and Thanks
 
@@ -157,8 +158,10 @@ The PIConGPU Team expresses its thanks to:
 - Anton Helm
 - Wolfgang Hoehnig
 - Dr. Remi Lehe
+- Felix Schmitt(*)
 - Benjamin Schneider
 - Joseph Schuchart
+- Conrad Schumann
 - Klaus Steiniger
 
 Kudos to everyone who helped!