Update README.rst

Author: abalijepalli

README.rst

@@ -6,6 +6,8 @@
 		:target: https://github.com/usnistgov/mosaic
 .. image:: https://img.shields.io/pypi/v/mosaic-nist.svg
 	:target: https://pypi.org/project/mosaic-nist/
+.. image:: https://img.shields.io/pypi/dm/mosaic-nist
+   	:target: https://pypi.org/project/mosaic-nist/
 .. image:: https://codecov.io/gh/usnistgov/mosaic/branch/master/graph/badge.svg
 	:target: https://codecov.io/gh/usnistgov/mosaic  
 .. image:: https://img.shields.io/badge/dev-NIST-blue