feat: add token approval type

Author: hmalik88

packages/keyring-api/src/api/transaction.ts

@@ -165,6 +165,11 @@ export enum TransactionType {
    */
   StakeWithdraw = 'stake:withdraw',
 
+  /**
+   * Represents a token approval transaction.
+   */
+  Approve = 'token:approve',
+
   /**
    * The transaction type is unknown. It's not possible to determine the
    * transaction type based on the information available.
@@ -355,6 +360,7 @@ export const TransactionStruct = object({
     `${TransactionType.BridgeReceive}`,
     `${TransactionType.StakeDeposit}`,
     `${TransactionType.StakeWithdraw}`,
+    `${TransactionType.Approve}`,
     `${TransactionType.Unknown}`,
   ]),