docs: add RepoCloud one-click deploy button

[cosark]

Adds RepoCloud as a one-click deployment option alongside the existing providers (Netlify, Vercel, Heroku, Qovery, Render, Railway, Koyeb, Zeabur).

RepoCloud provides managed cloud hosting for open-source applications with one-click deployment, automatic infrastructure provisioning, and free credits for new users.

• Adds deploy button to docs/Get started.md
• Adds table of contents entry in docs/Get started.md
• Adds navigation link in README.md
• Uses the same format/style as existing deploy buttons (Zeabur pattern)
• Links to: https://repocloud.io/details/Ackee/

[vercel]

@cosark is attempting to deploy a commit to the Tobias Reich's projects Team on Vercel.

A member of the Team first needs to authorize it.