added legal disclaimer to README.md (#471)

README.md

@@ -36,3 +36,22 @@ cd ..
 
 See the RRFS-Workflow User's guide:
 https://chanhoo-rrfs-workflow.readthedocs.io/en/latest/index.html
+
+## Disclaimer
+
+```
+The United States Department of Commerce (DOC) GitHub project code is
+provided on an "as is" basis and the user assumes responsibility for
+its use. DOC has relinquished control of the information and no longer
+has responsibility to protect the integrity, confidentiality, or
+availability of the information. Any claims against the Department of
+Commerce stemming from the use of its GitHub project will be governed
+by all applicable Federal law. Any reference to specific commercial
+products, processes, or services by service mark, trademark,
+manufacturer, or otherwise, does not constitute or imply their
+endorsement, recommendation or favoring by the Department of
+Commerce. The Department of Commerce seal and logo, or the seal and
+logo of a DOC bureau, shall not be used in any manner to imply
+endorsement of any commercial product or activity by DOC or the United
+States Government.
+