chore: update lock docs in readme and remove unused deps (#26)

* chore: update lock docs in readme

* chore: remove unused deps

Author: RetricSu

deps/README.md

@@ -15,12 +15,27 @@ const nostrPublicKey = '0x45c41f21e1cf715fa6d9ca20b8e002a574db7bb49e96ee89834c66
 const nostrLockScript = sdk.lock.buildScript(nostrPublicKey);
 const ckbAddress = sdk.lock.encodeToCKBAddress(nostrPublicKey);
 
-// signed a nostr-lock input transaction
+//**** Signed a nostr-lock input transaction ****//
+
+// construct a nostr signer first
 const signer = async (event: EventToSign) => {
   //...nostr signing event code
   const signedEvent: SignedEvent = //...
   return signedEvent;
 };
+// sdk.lock.signTx will overwrite the witness lock with dummyLock and then generate sigHashAll,
+// sign it and return signed transaction. It is a easy way to do nostr lock signing if
+// transaction fee estimation is not a problem to you. After calling this function, witness
+// is auto-filled with signedEvent.
 txSkeleton = await sdk.lock.signTx(txSkeleton, signer);
-// witness is auto-filled with signedEvent
+
+// or prepare your transaction first
+import { createTransactionFromSkeleton } from "@ckb-lumos/lumos/helpers";
+let tx = createTransactionFromSkeleton(txSkeleton);
+// fill-in the witness of nostr-lock with corresponding dummyLock
+tx = await sdk.lock.prepareTx(transaction: Transaction);
+// sdk.lock.signPreparedTx will checks if the transaction is placed with correct Nostr-lock dummyLock
+// and then directly generate sigHashAll from the giving transaction, sign it and return
+// signed transaction. You need to call prepareTx before this function.
+const signedTx = await sdk.lock.signPreparedTx(tx, signer);
 ```