Clarify "dual-licensed" (#351)

I pulled the additional text directly from #136 where @fge answered the question, "Do I need to abide by both licenses? Or can I pick which one to abide by?"

Adding it here in the LICENSE file to help avoid a need for anyone else to dive into closed issues to find the answer.

Author: ajorg-aws

Diff for: LICENSE

@@ -6,6 +6,7 @@ This software is dual-licensed under:
 
 The text of both licenses is included (under the names LGPL-3.0.txt and
 ASL-2.0.txt respectively).
+Should you choose to redistribute, you can pick either, or continue to dual license.
 
 Direct link to the sources: