[website] Add Avalanche Development Update blog post for Aug 2022

Summary: Summarizes improvements made since the last update

Test Plan:
Read it through, make sure it makes sense
Ran it locally, checked links

Reviewers: Fabien, sdulfari, #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D11824