Remove repo docs dirs and link to docs site

[aljo242]

Several code repos (SDK, IBC, EVM, etc.) have docs/ directories that are out of sync with the docs site repo, and edits in one don’t reflect in the other.

Proposal: remove the docs/ directories from those repos and add a docs.md file that links to the docs site. Confirm approach with the team before making changes.

[linear]

IBCSPEC-475