Update starter subscriptions documentation

Author: Gaurav agarwal

docs/start/starter-subscriptions.md

@@ -95,7 +95,9 @@ Monitor the balance and gas fee burnt for a particular address in real-time.
 
 ▶️ [Monitoring Balance after Latest Gas Fee Burn](https://ide.bitquery.io/Monitor-balance-and-gas-fee-paid-for-an-address-using-stream_1)
 
-### Token Supply
+### Token supply
+
+#### Monitor Token Supply
 
 Monitor Real time token supply in real time on Ethereum chain.