docs: add read-aloud support to MkDocs

[paolino]

Add read-aloud support to MkDocs documentation:

• Add extra_javascript entry for read-aloud.js from paolino/dev-assets
• Add mkdocs-speech step to deploy workflow for speech JSON generation
• Adds play/pause buttons to each doc section, voice selector

Reference implementation: lambdasistemi/cardano-mpfs-browser#3