docs: move homepage file to main repository

[HonkingGoose]

Changes:

• Delete homepage file from the docs repository
• Use docs/usage/index.md from renovatebot/renovate instead

Context:

This PR "moves" this file to the main repository:

• docs: move docs index/homepage file to main repo renovate#28751

[HonkingGoose]

My Codespace creation fails, due to strict mode warnings.

The recovery container GitHub then gives me does not run make for me. The recovery container probably misses some key program or configuration.

This means that I can not test if (or rather how badly) I'm breaking the docs site with the removal of the homepage file.

I expect stuff to break until we have the new docs homepage on the renovatebot/renovate repository though.

See:

• Allow Codespaces/Gitpod container startup, even if site build fails the --strict mode tests #463

[HonkingGoose]

Renovate updated us to the new renovatebot/renovate submodule, where the homepage is under docs/usage/index.md in the renovate repository.

After updating my branch so it's current with main, the tests pass! 🥳

I think this means we're good to go? 😄