Proposal for 2.2 version and tagging

[videlais]

Based on the TwineJS issue "Migrating Release Notes Archive into Reference", the Twine Cookbook", the release notes from Twine Cookbook 2.1 are being migrated into the Twine Reference.

Previously, I wasn't keeping track of changes using tags and releases, but it might make more sense to tag any incoming changes from the Twine Reference move as part of a 2.2.0 version and collect up the previous 2.1 work as its own version.