Add Google Doc for adding blog posts

[rzats]

In https://github.com/snowplow/snowplowanalytics.com/blob/develop/README.md#what-is-snowplowanalyticscom - neither a wiki nor a contributors guide exist.

[jbeemster]

Hey @yalisassoon - I created a link for the Wiki but would be good to get some content for it. The old documentation was a bit confused on this point...

[alexanderdean]

Do we really want to maintain a wiki here - do we expect many open-source contributors? We could probably just add a guide to fixing typos / adding blog posts in our Google Drive...

[yalisassoon]

No I don't think we do...

[jbeemster]

Cool will remove it from the repo then - lets change this to needing a Google document for how to add blog posts instead then?