[website] Add Tutorial for Avalanche Staking

Summary: Explanation and steps to help people generate the own Stake Proofs and run an Avalanche-enable node

Test Plan:
Helped people actually go through the steps, fixed parts that tripped them up
Ran the site locally, read it and checked links.

Reviewers: PiRK, Fabien, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D11929