Add RTD badge.

Author: dcherian

README.rst

@@ -2,6 +2,10 @@
     :target: https://binder.pangeo.io/v2/gh/xarray-contrib/cf-xarray/master?urlpath=lab
     :alt: Binder
 
+.. image:: https://img.shields.io/readthedocs/cf-xarray/latest.svg?style=for-the-badge
+    :target: https://cf-xarray.readthedocs.io/en/latest/?badge=latest
+    :alt: Documentation Status
+
 .. image:: https://img.shields.io/github/workflow/status/xarray-contrib/cf-xarray/CI?logo=github&style=for-the-badge
     :target: https://github.com/xarray-contrib/cf-xarray/actions
     :alt: GitHub Workflow CI Status
@@ -19,9 +23,6 @@
     :alt: Python Package Index
 
 .. If you want the following badges to be visible, please remove this line, and unindent the lines below
-	.. image:: https://img.shields.io/readthedocs/cf-xarray/latest.svg?style=for-the-badge
-        :target: https://cf-xarray.readthedocs.io/en/latest/?badge=latest
-        :alt: Documentation Status
 
 	.. image:: https://img.shields.io/conda/vn/conda-forge/cf-xarray.svg?style=for-the-badge
         :target: https://anaconda.org/conda-forge/cf-xarray