add: Minimum Hardware Requirements

[alebanzas]

I would add Minimum Hardware Requirements section or page.

This article mentions it, but it could be outdated:
https://etherworld.co/2021/03/11/how-to-become-an-eth2-validator-on-teku/#minimumhardwarerequirements

Other clients with this info in their doc:
EL:

• https://docs.nethermind.io/nethermind/first-steps-with-nethermind/system-requirements
• https://besu.hyperledger.org/en/stable/public-networks/get-started/system-requirements/
• https://github.com/ledgerwatch/erigon#system-requirements
• https://geth.ethereum.org/docs/interface/hardware

CL:

• https://lighthouse-book.sigmaprime.io/system-requirements.html
• https://chainsafe.github.io/lodestar/#specifications
• https://nimbus.guide/hardware.html
• https://docs.prylabs.network/docs/install/install-with-script/#step-1-review-prerequisites-and-best-practices