Add testing page

[rheitjoh]

Figuring out whether the libraries offer any existing tests for your schemes is currently fairly difficult without consulting our own tests.

For example, to use the standalone tests you need to add the math-tests dependency to your project and then correctly use the standalone test. Similarly for the Craco tests via craco-tests.

It would be nice if we had a page that

• tells the user what kind of testing classes we offer
• how to access them
• how to use them

I originally started on something like this and then stopped, because I wanted to make the tests more uniform first (see this issue). I still think that should be addressed first (especially the signature tests). However, since the standalone tests have been rewritten already, one could at least write something for those.