Update README.md, add read the docs link

Author: skbarber

README.md

@@ -2,7 +2,9 @@
 Add-ons for the Generalized Equipment and Experiment Control system-
 
 Documentation at 
-https://sites.google.com/a/lbl.gov/geecs/plugins?authuser=0
+https://sites.google.com/a/lbl.gov/geecs/plugins?authuser=0 (original)
+
+read the docs: https://geecs-plugins.readthedocs.io/en/latest/
 
 *** Copyright Notice ***
 
@@ -16,4 +18,4 @@ If you have questions about your rights to use or distribute this software, plea
 
 NOTICE.  This Software was developed under funding from the U.S. Department of Energy and the U.S. Government consequently retains certain rights. As such, the U.S. Government has been granted for itself and others acting on its behalf a paid-up, nonexclusive, irrevocable, worldwide license in the Software to reproduce, distribute copies to the public, prepare derivative works, and perform publicly and display publicly, and to permit other to do so.
 
- 
+