add windows + linux instructions for the release checklist
add windows + linux instructions for the release checklist

blockstack/blockstack-browser,blockstack/blockstack-portal,blockstack/blockstack-browser,blockstack/blockstack-browser,blockstack/blockstack-portal,blockstack/blockstack-browser,blockstack/blockstack-browser,blockstack/blockstack-portal,blockstack/blockstack-portal,blockstack/blockstack-browser,blockstack/blockstack-portal