Published on Chrome Web Store: https://chrome.google.com/webstore/detail/gmail-to-trello/oceoildfbiaeclndnjknjpfaoofeekgl?hl=en
Support, commonly asked questions, interaction with other GtT fans: https://trello.com/b/CGU9BYgd/gmail-to-trello-extension
There are some additional useful documents in ./docs folder.