mynt 🍬 - a refreshing error handling crate for proc macros

mynt provides a straightforward way to handle errors based on the nightly diagnostic interface. It takes a different approach compared to manyhow.

Instead of returning results, we return token streams and instead emit errors externally and continue, only quitting if the error is fatal.

There is no passing around emitters or writing to dummy streams if an error occurs.

It is inspired by proc-macro-error3, but with some changes:

• Uses declarative macros instead of procedural macros for lower compile times
• All dependencies are optional
• Removes dummy streams (instead opting for the developer to emit as much as possible)
• Support for syn and proc-macro2, as well as support for venial and darling
• Macros for emitting diagnostics, bailing, quitting, and writing assertions
• Terminal colors for the stable channel fallback with yansi