[Enhancement]: Add Infura Sepolia Faucet link

### What would you like us to improve?

I have added Infura Sepolia faucet link 

### How important it is?

Users referring to the documentation now can use Infura Sepolia faucet to request SepEth and test Scroll ecosystem. Also to note that Infura Sepolia faucet is also reliable with minimal downtimes.