Switch to BSD License

Authlib will be released under BSD license from next release.

This is an announcement - license for Authlib will be switched from APGL to BSD from v0.11.

The [license issue][] has been there for a long time. APGL has prevented many people from using Authlib, it is a time to make a change. Authlib will be licensed under BSD from next release v0.11.

The commercial license is still available. New commercial plans will be listed on the pricing page.

Happy new license, happy new year.

Here is the GitHub commit.

[license issue]: https://github.com/lepture/authlib/issues/59