Add "Unsafe Forbidden" Badge to the README
<img src="https://img.shields.io/badge/docs-latest-blue.svg?style=flat-square"
alt="docs.rs docs" />
</a>
+ <a href="https://github.com/rust-secure-code/safety-dance/">
+ <img src="https://img.shields.io/badge/unsafe-forbidden-success.svg?style=flat-square"
+ alt="Unsafe Rust forbidden" />
+ </a>
</div>
`Async-graphql` is a high-performance server-side library that supports all GraphQL specifications.
