WIP(account): update README.md

packages/harmony-account/README.md

@@ -7,6 +7,7 @@
       2. [import an existing privateKey to create Account](#import-an-existing-privatekey-to-create-account)
       3. [Encrypt/Export keyStore file, Decrypt/Import keyStore file](#encryptexport-keystore-file-decryptimport-keystore-file)
       4. [Address format getter](#address-format-getter)
+      5. [Sign a transaction](#sign-a-transaction)
 3. [Usage of Wallet](#usage-of-wallet)
    1. [Dependencies](#dependencies-1)
 
@@ -51,9 +52,9 @@ The `Wallet` class is class that stores all `Account` instance, you can do CRUD
 
     // create a custom messenger
     const customMessenger = new Messenger(
-    new HttpProvider('http://localhost:9500'),
-    ChainType.Harmony, // if you are connected to Harmony's blockchain
-    ChainID.HmyLocal, // check if the chainId is correct
+        new HttpProvider('http://localhost:9500'),
+        ChainType.Harmony, // if you are connected to Harmony's blockchain
+        ChainID.HmyLocal, // check if the chainId is correct
     )
 
     // to create an Account with random privateKey
@@ -174,6 +175,68 @@ The `Wallet` class is class that stores all `Account` instance, you can do CRUD
 ```
 
 
+### Sign a transaction
+
+```typescript
+
+    // import the Account class
+    import {Account} from '@harmony-js/account'
+
+    // import Transaction class from '@harmony-js/transaction'
+    import {Transaction} from '@harmony-js/transaction'
+    
+     // Messenger is optional, by default, we have a defaultMessenger 
+    // If you like to change, you will import related package here.
+    import { HttpProvider, Messenger } from '@harmony-js/network';
+    import { ChainType, ChainID, Unit } from '@harmony-js/utils';
+
+    // create a custom messenger
+    const customMessenger = new Messenger(
+        new HttpProvider('http://localhost:9500'),
+        ChainType.Harmony, // if you are connected to Harmony's blockchain
+        ChainID.HmyLocal, // check if the chainId is correct
+    )
+    // suppose we have an account
+    const myPrivateKey = '0xe19d05c5452598e24caad4a0d85a49146f7be089515c905ae6a19e8a578a6930'
+    const myAccountWithMyPrivateKey = new Account(myPrivateKey)
+
+    
+    const txnObject = {
+        //  token send to
+        to: 'one166axnkjmghkf3df7xfvd0hn4dft8kemrza4cd2',
+        // amount to send
+        value: '1000000000000000000000',
+        // gas limit, you can use string or use BN value
+        gasLimit: '210000',
+        // send token from shardID
+        shardID: 0,
+        // send token to toShardID
+        toShardID: 0,
+        // gas Price, you can use Unit class, and use Gwei, then remember to use toWei(), which will be transformed to BN
+        gasPrice: new Unit('100').asGwei().toWei(),
+        // if you set nonce manually here, and remember, the `updateNonce` of `Account.signTransaction` should be set to false
+        nonce: 0,
+    };
+
+    const txn = new Transaction(txnObject, customMessenger);
+
+    async function signTheTxn() {
+        // Account.signTransaction(transaction: Transaction, updateNonce?: boolean, encodeMode?: string, blockNumber?: string): Promise<Transaction>
+        // If the 2nd parameter `updateNonce` is set to true, it will query and update account's nonce before it signs
+        const signedTxn = await myAccountWithMyPrivateKey.signTransaction(txn, false, 'rlp', 'latest');
+
+        // see if the transaction is signed
+        console.log(`\n see if transaction is signed: \n ${signedTxn.isSigned()} \n`);
+
+        // get the tranaction bytes
+        console.log(`\n the signed bytes is: \n ${signedTxn.getRawTransaction()} \n`);
+
+        return signTheTxn;
+    }
+
+    signTheTxn();
+```
+
 
 # Usage of Wallet