Dear Maintainer,

I've been depending on the catch2 library package for newsboat which by default
vendors the catch library. To be compatible with the Debian policy I have
overridden this so that the packaged version is used instead.

However with version 3 now there are separate header files for each function and
since upstream is relying on the single header/amalgamated version it is not
easy to patch to include all the required functionalities.

It'd be great to also generate and include the amalgamated header file
(generation script can be found here[1]) in order to ease the version 3
transition for amalgamated header users.

[1] https://github.com/catchorg/Catch2/blob/fa5a53df17303339eff8fda5cae0b601af207085/tools/scripts/generateAmalgamatedFiles.py

Cheers,
Nikos