chore(license): 🔧 add MIT license to the repo

[johnDeSilencio]

What?

This PR adds the MIT License in a LICENSE file to the repository with the current year and the repository owner's full name in the header of the file.

Why?

It is a good idea to always license repositories so that other people and organizations can use your work without fear of the legal risk associated with making changes and distributing changes. The best and most recent example I can think of is the dust DS emulator from the Rust ecosystem. This repository did not have a license associated with it, and so when it was unexpectedly deleted, none of the existing forks could be used to continue development. To minimize the legal risk of using code and examples from this repository, it would be very helpful if it had an open-source license.

I went to your website to get your full name and place it in the author field of the license. If you would like your name to appear differently than Percy Bolmér in the license file, feel free to edit this PR.

I chose MIT because I feel it's the easiest to work with; out of all the licenses, it "stays out of the way" the best. If you would rather use a different license, feel free to make edits to this PR.

Lastly, I wanted to say thank you for your informative video as it has helped me and my colleagues greatly get to understand the complexity of managing multiple WebSocket connections. Keep up the great work 😃

[johnDeSilencio]

@percybolmer let me know if you have any feedback for this PR!