Use `mkdocs-macros` to get the current version for the docs

[llucax]

What's needed?

The docs are sometimes getting outdated in the examples on how to create a project based on the cookiecutter template, as we are using a tag for checkout.

Proposed solution

Get the current version automatically by using mkdocs-macros, which provide easy access to the git info:

• https://mkdocs-macros-plugin.readthedocs.io/en/latest/git_info/

Example on setting up mkdocs-macros:

• Add mkdocs-macros plugin frequenz-sdk-python#667

Use cases

No response

Alternatives and workarounds

No response

Additional context

No response