make Msg type generic in msg.data

lib/msg-v3/index.js

@@ -29,18 +29,11 @@ const { isEmptyObject } = require('./util')
  * @typedef {import('ppppp-keypair').Keypair} Keypair
  */
 
+
 /**
- * @typedef {Iterator<Msg> & {values: () => Iterator<Msg>}} MsgIter
+ * @template [T=any]
- *
- * @typedef {Buffer | Uint8Array} B4A
- *
  * @typedef {{
- *   depth: number;
+ *   data: T;
- *   prev: Array<string>;
- * }} TangleMetadata
- *
- * @typedef {{
- *   data: any;
  *   metadata: {
  *     dataHash: string | null;
  *     dataSize: number;
@@ -53,6 +46,17 @@ const { isEmptyObject } = require('./util')
  *   pubkey: string;
  *   sig: string;
  * }} Msg
+ */
+
+/**
+ * @typedef {Iterator<Msg> & {values: () => Iterator<Msg>}} MsgIter
+ *
+ * @typedef {Buffer | Uint8Array} B4A
+ *
+ * @typedef {{
+ *   depth: number;
+ *   prev: Array<string>;
+ * }} TangleMetadata
  *
  * @typedef {{
  *   action: 'add', add: AccountAdd