Add rough draft of hashlock contract

src/test/contracts/hashlock.mligo

@@ -0,0 +1,16 @@
+type storage = {
+  hashed: bytes;
+  unused: bool;
+}
+
+type parameter = {
+  hashable: bytes;
+  message: unit -> operation list;
+}
+
+let main ((p,s): parameter * storage) : operation list * storage =
+  if ((Crypto.sha256 p.hashable) = s.hashed) && s.unused
+  then
+    let s: storage = {hashed = s.hashed; unused = false} in
+    ((p.message ()), s)
+  else (([]: operation list), s)