chore: update README.md

Signed-off-by: Wenhao Ho <[email protected]>

README.md

@@ -40,6 +40,7 @@ To configure your Ubiquibot to run this plugin, add the following to the `.ubiqu
     taskStaleTimeoutDuration: "30 Days"
     maxConcurrentTasks: 3
     startRequiresWallet: true # default is true
+    emptyWalletText: "Please set your wallet address with the /wallet command first and try again."
 ```
 
 # Testing