NOTICE.LLNS: add required LLNS release notice

Add release notice text per
https://software.llnl.gov/about/licenses/

NOTICE.LLNS

@@ -0,0 +1,21 @@
+This work was produced under the auspices of the U.S. Department of
+Energy by Lawrence Livermore National Laboratory under Contract
+DE-AC52-07NA27344.
+
+This work was prepared as an account of work sponsored by an agency of
+the United States Government. Neither the United States Government nor
+Lawrence Livermore National Security, LLC, nor any of their employees
+makes any warranty, expressed or implied, or assumes any legal liability
+or responsibility for the accuracy, completeness, or usefulness of any
+information, apparatus, product, or process disclosed, or represents that
+its use would not infringe privately owned rights.
+
+Reference herein to any specific commercial product, process, or service
+by trade name, trademark, manufacturer, or otherwise does not necessarily
+constitute or imply its endorsement, recommendation, or favoring by the
+United States Government or Lawrence Livermore National Security, LLC.
+
+The views and opinions of authors expressed herein do not necessarily
+state or reflect those of the United States Government or Lawrence
+Livermore National Security, LLC, and shall not be used for advertising
+or product endorsement purposes.