Add README.md to smt2_strings

Author: Joel Allred

regression/smt2_strings/README.md

@@ -0,0 +1,14 @@
+Test Suite for SMT2 String Operations
+=====================================
+
+The purpose of this suite is to test the level of string support of cbmc's smt2
+backend.
+
+It can also be used to test the level of string support of any smt2 solver, by
+using a command such as:
+```
+../test.pl -p -F -c <path_to_solver_binary>
+```
+
+(note the `-F` option to consider all tests tagged as "FUTURE").
+