Introduction to C++20 concepts

Welcome the the next GRCPP meetup where we will introduce a powerful new feature in C++20: Concepts.

Concepts are a way to specify requirements on template parameter types and to make templates more expressive and easier to understand..
We will show how to use concepts to create "interfaces" for your template types, how to simplify your code and provide better error messages.
We will demonstrate how to use `requires` to create "contracts" for your templates and how to use `concept` to constrain the acceptable types.

We will assume that you know the fundamentals of C++ templates but you are welcome to join nonetheless.