Document Semantic Versioning Best Practice

[mgifford]

Git offers semantic versioning - https://github.com/marketplace/actions/git-semantic-version

Not sure the most non-technical explanation of this but perhaps - https://medium.com/swlh/automatic-semantic-versioning-by-using-gitversion-9e22edecb116

Given that the important thing is to align with products and services, we should think through a few common scenarios and document them.

Dev versions

Many accessibility issues are identified and fixed in alpha, git or development versions of the code, prior to a formal release. If the issue queues are integrated with an OPAT then we are going to see issues which are on versions which are not yet fully baked.

Issues found post-release

It's normal to get users reporting issues against a particular release of the software. The bug might exist in version 2.3.2.1 but was mitigated in one way or another in 2.3.3.0. Either way, it is useful to add a bug to the earlier release so that it can be included in a comprehensive ACR.

SASS

It could be that there are multiple versions which have some differences between them which we would want to capture.

[mgifford]

Related to #269