docs: Add page on decentralized AI inference

[ielashi]

Most of the content is taken from the overview page and moved/reorganized into an inference page that we can evolve over time.

I moved the examples into the inference tab in the sidebar as well, as they are inference examples.

[github-actions[bot]]

🤖 Here's your preview: https://fkpod-biaaa-aaaam-abtcq-cai.icp0.io

[ielashi]

@jessiemongeon1 I should have addressed all your points. PTAL.