Add CITATION.cff file (#20)

* Add CITATION.cff file

So that people know how to cite the short course.

* Add Zenodo DOI to CITATION.cff file

Finally reserved a DOI on Zenodo for this short course!

* Add conference name and country

Not sure if this will show up in the reference, and technically this was presented virtually instead of in Austria where EGU is usually held, but let's go with this.

Author: weiji14

CITATION.cff

@@ -0,0 +1,36 @@
+# This CITATION.cff file was generated with cffinit.
+# Visit https://citation-file-format.github.io to generate yours today!
+
+cff-version: 1.2.0
+title: Crafting beautiful maps with PyGMT
+message: >-
+  If you use this short course, please cite it as
+  below.
+authors:
+  - given-names: Wei Ji
+    family-names: Leong
+    affiliation: 'The Ohio State University, USA'
+    orcid: 'https://orcid.org/0000-0003-2354-1988'
+  - given-names: Leonardo
+    family-names: Uieda
+    affiliation: 'University of Liverpool, United Kingdom'
+    orcid: 'https://orcid.org/0000-0001-6123-9515'
+  - given-names: Max
+    family-names: Jones
+    affiliation: 'CarbonPlan, USA'
+    orcid: 'https://orcid.org/0000-0003-0180-8928'
+  - given-names: André
+    family-names: Belém
+    affiliation: 'Universidade Federal Fluminense, Brazil'
+    orcid: 'https://orcid.org/0000-0002-8865-6180'
+date-released: '2022-05-24'
+doi: 10.5281/zenodo.1003149
+license: CC-BY-4.0
+references:
+  - conference:
+      name: "EGU General Assembly 2022"
+      country: AT
+repository-code: 'https://github.com/GenericMappingTools/egu22pygmt'
+type: software
+url: 'https://www.generic-mapping-tools.org/egu22pygmt'
+version: 1.0.0