Prove binary soundness for Fμ,ref,par

There is one admit that needs to be taken care of. The admitted case is validity
of a monoid element of iprod. At the moment iris doesn't seem to have necessary
lemmas to prove this easily.

_CoqProject

@@ -26,4 +26,5 @@ F_mu_ref_par/fundamental_unary.v
 F_mu_ref_par/rules_binary.v
 F_mu_ref_par/logrel_binary.v
 F_mu_ref_par/fundamental_binary.v
-F_mu_ref_par/soundness_unary.v
\ No newline at end of file
+F_mu_ref_par/soundness_unary.v
+F_mu_ref_par/soundness_binary.v
\ No newline at end of file