Add CITATION.cff for the nf-core publication

CITATION.cff

@@ -0,0 +1,56 @@
+cff-version: 1.2.0
+message: "If you use `nf-core tools` in your work, please cite the `nf-core` publication"
+authors:
+  - family-names: Ewels
+    given-names: Philip
+  - family-names: Peltzer
+    given-names: Alexander
+  - family-names: Fillinger
+    given-names: Sven
+  - family-names: Patel
+    given-names: Harshil
+  - family-names: Alneberg
+    given-names: Johannes
+  - family-names: Wilm
+    given-names: Andreas
+  - family-names: Ulysse Garcia
+    given-names: Maxime
+  - family-names: Di Tommaso
+    given-names: Paolo
+  - family-names: Nahnsen
+    given-names: Sven
+title: "The nf-core framework for community-curated bioinformatics pipelines."
+version: 2.4.1
+doi: 10.1038/s41587-020-0439-x
+date-released: 2022-05-16
+url: https://github.com/nf-core/tools
+prefered-citation:
+  type: article
+  authors:
+    - family-names: Ewels
+      given-names: Philip
+    - family-names: Peltzer
+      given-names: Alexander
+    - family-names: Fillinger
+      given-names: Sven
+    - family-names: Patel
+      given-names: Harshil
+    - family-names: Alneberg
+      given-names: Johannes
+    - family-names: Wilm
+      given-names: Andreas
+    - family-names: Ulysse Garcia
+      given-names: Maxime
+    - family-names: Di Tommaso
+      given-names: Paolo
+    - family-names: Nahnsen
+      given-names: Sven
+  doi: 10.1038/s41587-020-0439-x
+  journal: nature biotechnology
+  start: 276
+  end: 278
+  title: "The nf-core framework for community-curated bioinformatics pipelines."
+  issue: 3
+  volume: 38
+  year: 2020
+  url: https://dx.doi.org/10.1038/s41587-020-0439-x