Automatize creating "run online" links for new releases

We used to have a "run online" link to WandBox instance with uploaded single header, small main and a test file, so the users could play around with Catch2 online, without downloading it, setting up a development environment and so on.

Due to various reasons, we do not have this link up anymore (there were issues with WandBox's reliability IIRC, and our "single header" got too big to upload), but we can use Compiler Explorer instead.

However, we will not be uploading Catch2 sources to a Compiler Explorer session, instead we will be using their precompiled static library version. AFAIK it should be possible to autogenerate a link that initializes CE session with specific libraries linked, in our case with the new release of Catch2, that will work once CE picks up the new release (which should happen every midnight).