Merge other basic circuits here

test/circuits/constants_test.circom

@@ -0,0 +1,18 @@
+include "../../circuits/sha256/constants.circom"
+
+template A() {
+    signal input in;
+    component h0;
+    h0 = K(8);
+
+    var lc = 0;
+    var e = 1;
+    for (var i=0; i<32; i++) {
+        lc = lc + e*h0.out[i];
+        e *= 2;
+    }
+
+    lc === in;
+}
+
+component main = A();