Add credits for Gemini

closes #670

Author: hamogu

credits.html

@@ -275,6 +275,12 @@ <h3 id="numfocus">NumFOCUS</h3>
 organizational support to grow Astropy into the role of a community-leading
 project with a substantial budget.
 
+<h3 id="gemini">Gemini</h3>
+The Science User Support Department at the Gemini Observatory has supported work
+on both the Astropy and DRAGONS projects. This support has happened by funding staff members
+who can contribute to Astropy development, and by providing funding for developers
+on the Astropy project.
+
 <h3 id="cca-flatiron-simons-foundation">Center for Computational Astrophysics (CCA), Flatiron Institute, Simons
 Foundation</h3>
 The CCA has provided logistical and travel support for the Python in Astronomy