Add Sanic to readme

[mmaybeno]

I feel there are plenty more frameworks that are not on this list yet. Sanic is one I know for sure. :)

Checklist

• This project is explicitly related to ASGI.
• The new list entry contains project name, URL and description.

What is this project?

Sanic is a Python 3.6+ web server and web framework that's written to go fast. It allows the usage of the async/await syntax added in Python 3.5, which makes your code non-blocking and speedy. Supports HTTP and WebSockets.

Do you know about other similar projects?

Yes

If so, how is this one different?

This one is different specifically as it is not by the encode team

Anyone who agrees with this pull request can add a 👍.

[florimondmanca]

Sounds good to me! I wasn't aware Sanic supported ASGI 3 when I wrote down the first list of ASGI web frameworks. Thanks. :)

[mmaybeno]

Yep not sure when they added it but glad they did :)

[florimondmanca]

Thank you 🎉