Suggestion: document a simpler CMake integration via FetchContent about doctest HOT 2 OPEN

Ah, my issue search skills are obviously pretty bad, thank you!
However, the approach suggested in #698 and implemented in #821 is still suboptimal for doctest unless one needs doctest_discover_tests(<target>) functionality.
It works but it clones the GitHub repo and perform CMake configure on it. The library is a single header and none of it is really necessary.
The approach above is bare-bones and faster - only a single header is downloaded and no configuration is performed at all.

Thank you!

from doctest.

Relevant:
#698
#821

I guess there's a few ways of doing it

from doctest.