hello world for starters

examples/hello_world/validators/hello_world.ak

@@ -0,0 +1,22 @@
+use aiken/hash.{Blake2b_224, Hash}
+use aiken/list
+use aiken/string
+use aiken/transaction.{ScriptContext}
+use aiken/transaction/credential.{VerificationKey}
+
+pub type Datum {
+  owner: Hash<Blake2b_224, VerificationKey>,
+}
+
+pub type Redeemer {
+  msg: ByteArray,
+}
+
+pub fn spend(datum: Datum, redeemer: Redeemer, context: ScriptContext) -> Bool {
+  let must_say_hello = string.from_bytearray(redeemer.msg) == "Hello, World!"
+
+  let must_be_signed =
+    list.has(context.transaction.extra_signatories, datum.owner)
+
+  must_say_hello && must_be_signed
+}