Show UXarray calendar on docs sidebar (#1506)

* Create a calendar page and show UXarray calendar in it

* Fix calendar not whowing up issue

* Fix calendar not whowing up issue

Author: erogluorhan

docs/calendar.rst

@@ -0,0 +1,15 @@
+.. currentmodule:: uxarray
+
+.. _calendar:
+
+***************
+Events Calendar
+***************
+
+Please find the public monthly community meetings and other events in the
+calendar below and join us once or regularly with whichever of them works
+best for you:
+
+.. raw:: html
+
+   <iframe src="https://calendar.google.com/calendar/embed?src=c_aded7956c547d66408841073b714d36d98955376d40f43f32efb1d6bad3b9824%40group.calendar.google.com&ctz=America%2FDenver" style="border: 0" width="800" height="600" frameborder="0" scrolling="no"></iframe>

docs/index.rst

@@ -113,6 +113,7 @@ around the `UGRID <http://ugrid-conventions.github.io/ugrid-conventions/>`_ conv
     GitHub Issues <https://github.com/UXARRAY/uxarray/issues>
     UGRID Conventions <https://ugrid-conventions.github.io/ugrid-conventions/>
     contributing
+    calendar
 
 .. raw:: html