[Improvement] Improve the clarity of versions of the specification

[eelcodenheijer]

Describe the improvement

The documentation of the Shapeshifter specification is not always entirely clear on what version it is supposed to be; for instance: the online browsable specification https://shapeshifter.github.io/shapeshifter-specification/development/ has the development version (this is suggested in the URL), but in the upper right corner it denotes 3.0.0 which suggests that this is the current released version.

There is a pulldown for the version (I think) but the only option is Development.

Expected behavior

• Add the version to the generated PDF (preferably in the header or footer); if you are not sure about the version, at least clearly indicate that this is not the released version
• Add the released version to the browsable version, clearly indicating that you are looking at the released version (in the upper right corner, and preferably also in the generated PDF)

Screenshots

[nicorikken]

Indeed. We need to make a GitHub Release (v.3.0.1, v3.1.0 or v4.0.0) and then the workflow should automatically build and publish a new page.