Migrate from MKDocs to Zensical

## Description
Material for MKDocs was placed into maintenance mode on November 6th, 2025, as its authors have shifted their focus to a new framework: Zensical.

## Context
The Kedro team is looking into migrating as well and will answer all the relevant questions. See kedro-org/kedro#5267.

## Possible Implementation
It might be a good idea to let the Kedro team migrate first.