Document new pinning service pinion.build

pinion.build is a relative newcomer to the ecosystem.

We would like to add documentation to the project in line with other documentation we see about other services.

We are building something very cool using IPFS, and we would like to see our name next to other cool projects.

Today, Pinion can be used to pin and manage content on IPFS, write data directly through its gateway, and automatically
publish content from GitHub repositories. It is designed to be easy to integrate into existing workflows while offering
competitive pricing.

You're welcome to checkout our documentation for what we have built, and our "minions" page to see what we're working on next.

If you do have any questions about us or about the documentation PRs you can reach out to me directly, using the contact information on the website,
or book a call.