Citation metadata (#1452)

* skyfield_data updated

* initial Citation metadata file

* christian added

* improved Marcs affiliation

* cite all AUTHORS

CITATION.cff

@@ -0,0 +1,36 @@
+cff-version: "1.2.0"
+contact: 
+    - website: https://github.com/Open-MSS/MSS/wiki/Contact
+      name: "MSS community"
+license: "Apache-2.0"
+title: "Mission Support System Software"
+abstract: "A client/server application developed in the community to collaboratively create flight plans based on model data."
+message: "If you like to credit this software, please use this citation."
+type: "software"
+authors:
+  - affiliation: "Forschungszentrum Jülich GmbH"
+    family-names: "Bauer"
+    given-names: "Reimar"
+    email: "rb.proj@gmail.com"
+    orcid: "https://orcid.org/0000-0001-8663-911X"
+  - affiliation: "Forschungszentrum Jülich GmbH"
+    family-names: "Ungermann"
+    given-names:  "Jörn"
+    email: "j.ungermann@fz-juelich.de"
+    orcid:  "https://orcid.org/0000-0001-9095-8332"
+  - affiliation: "Forschungszentrum Jülich GmbH"
+    family-names: "Grooß" 
+    given-names: "Jens-Uwe"
+    email: "j.-u.grooss@fz-juelich.de"
+    orcid: "https://orcid.org/0000-0002-9485-866X"
+  - affiliation: "Forschungszentrum Jülich GmbH"
+    family-names: "Rolf"
+    given-names: "Christian"
+    email: "c.rolf@fz-juelich.de"
+    orcid: "https://orcid.org/0000-0001-5329-0054"
+  - affiliation: "Universität Hamburg"
+    family-names: "Rautenhaus"
+    given-names: "Marc"
+    email: "marc.rautenhaus@uni-hamburg.de"
+    orcid: "https://orcid.org/0000-0002-2715-2165"
+  - name: "MSS AUTHORS"