`mkdocs-material` docs generation package EOL

[ponyisi]

The following appeared in a recent dependabot update (#1220 ):

mkdocs-material-9.7.0
[!WARNING]

Material for MkDocs is now in maintenance mode

This is the last release of Material for MkDocs that will receive new features. Going forward, the Material for MkDocs team focuses on Zensical, a next-gen static site generator built from first principles. We will provide critical bug fixes and security updates for Material for MkDocs for 12 months at least.

Not an immediate concern but I guess we will need to consider our options at some point.