Add beman.scope into Compiler Explorer

Add beman.scope library into Compiler Explorer

beman.scope is a library within the [Beman Project](https://www.bemanproject.org/), used by WG21 to get implementation experience for proposed library features for C++ latest versions.

The library can be found at https://github.com/bemanproject/scope

Beman Issue - https://github.com/bemanproject/scope/issues/22