Usage and Setup sections (#348)

* Add details on usage section

* Start adding Ethereum testnet section

* Complete setup section

* Fix Mainnet image link

* Fix Aligned fork branch

* Add staking step in Testnet setup

* Complete Aligned Testnet setup

* Update README.md

* Revert "Update README.md"

This reverts commit 2f68a5d.

* Update submit state command

* Fix Testnet setup ordered list

* Update batcher deployment result paragraph

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Co-authored-by: Estéfano Bargas <[email protected]>