Update DOI and version number for v0.6.0 (#1817)

* Fix version number to 0.6.0
* Update CITATION.cff
* Update README.rst

Co-authored-by: Meghan Jones <meghanj@alum.mit.edu>

Author: michaelgrund

CITATION.cff

@@ -64,9 +64,9 @@ authors:
   family-names: Wessel
   affiliation: University of Hawai'i at Mānoa, USA
   orcid: https://orcid.org/0000-0001-5708-7336
-date-released: 2021-10-29
-doi: 10.5281/zenodo.5607255
+date-released: 2022-03-14
+doi: 10.5281/zenodo.6349217
 license: BSD-3-Clause
 repository-code: https://github.com/GenericMappingTools/pygmt
 type: software
-version: 0.5.0
+version: 0.6.0

README.rst

@@ -156,7 +156,7 @@ Developers". Feel free to cite our work in your research using the following Bib
 
 .. code-block::
 
-    @software{pygmt_2021_5607255,
+    @software{pygmt_2022_6349217,
       author       = {Uieda, Leonardo and
                       Tian, Dongdong and
                       Leong, Wei Ji and
@@ -173,12 +173,12 @@ Developers". Feel free to cite our work in your research using the following Bib
                       Quinn, Jamie and
                       Wessel, Paul},
       title        = {{PyGMT: A Python interface for the Generic Mapping Tools}},
-      month        = oct,
-      year         = 2021,
+      month        = march,
+      year         = 2022,
       publisher    = {Zenodo},
-      version      = {v0.5.0},
-      doi          = {10.5281/zenodo.5607255},
-      url          = {https://doi.org/10.5281/zenodo.5607255}
+      version      = {v0.6.0},
+      doi          = {10.5281/zenodo.6349217},
+      url          = {https://doi.org/10.5281/zenodo.6349217}
     }
 
 To cite a specific version of PyGMT, go to our Zenodo page at