Added ref to mainnet addresses in staking guide

Author: LandauRaz

components/Starknet/modules/guides/pages/staking-on-starknet/stake.adoc

@@ -11,6 +11,12 @@ Welcome to the second installment of the _Becoming a Starknet validator_ guide!
 
 To become a validator, you must stake least the minimum required amount of STRK tokens by locking them into Starknet's Staking contract, subsequentially earning rewards based on your participation. This installment of the guide will therefore walk you through xref:approving_strk_transfer[approving a transfer of STRK tokens to the Staking contract], xref:locking_strk[locking them into it], and xref:verifying_stakes[verifying that the procedure was successful].
 
+[TIP]
+====
+The steps in this installment are demonstrated on Sepolia.
+
+For the equivalent addresses on Mainnet, see xref:resources:chain-info.adoc#important_addresses[Chain information]. 
+====
 
 == Approving STRK transfer