Removal of non-inclusive terminology from Ably codebases

Ably, a tech company, has decided to remove terminology such as "master" and "slave" from their software in an effort to promote anti-racism within their organization and the wider tech community. They will begin by renaming the "master" branch on their public repositories to "main", with updates to internal codebases following over the next few weeks. Additionally, they have prepared a cheatsheet to aid adoption of these practices in relation to git. The company acknowledges that there is much more to learn and will continue to support the anti-racist movement.