feat: signing order (#1290)

Adds the ability to specify an optional signing order for documents.
When specified a document will be considered sequential with recipients
only being allowed to sign in the order that they were specified in.

apps/web/src/app/embed/paywall.tsx

@@ -1,5 +1,7 @@
 export const EmbedPaywall = () => {
-  return <div>
-    <h1>Paywall</h1>
-  </div>
-}
+  return (
+    <div>
+      <h1>Paywall</h1>
+    </div>
+  );
+};