zkas/zk: add sparse_tree_is_member() opcode

proof/smt.zk

@@ -0,0 +1,21 @@
+k = 13;
+field = "pallas";
+
+constant "SMT" {
+}
+
+witness "SMT" {
+    Base root,
+    SparseMerklePath path,
+    Base leaf,
+}
+
+circuit "SMT" {
+    is_member = sparse_tree_is_member(root, path, leaf);
+
+    ONE = witness_base(1);
+    constrain_equal_base(is_member, ONE);
+
+    constrain_instance(root);
+}
+