Guardfile in rbnacl-5.0.0 vs Guardfile in rbnacl-6.0.0

@@ -1,4 +1,6 @@
+# frozen_string_literal: true
+
 # A sample Guardfile
 # More info at https://github.com/guard/guard#readme
 
 guard :rspec do
   watch(%r{^spec/.+_spec\.rb$})