meson include directory

[Jakob Widauer]

Description

Hi there!
I've been using doctest for quite a while using CMake and Conan and have been loving it!
I was now trying to use it directly as a meson subproject.
While doing so, I noticed that in the current meson.build file, it declares the dependency to directly include the doctest directory.
It's specifically this line:

doctest_dep = declare_dependency(include_directories: include_directories('doctest'))

This means that, to be able to use doctest from a meson project, one would have to include it like this:

#include <doctest.h>

Instead of the way that is shown in the examples and done for all the other build systems:

#include <doctest/doctest.h>

Is this intended?
If not, I would assume the above line in the meson.build file to be:

doctest_dep = declare_dependency(include_directories: include_directories('.'))

Steps to reproduce

Try and use doctest as a subproject in a project using meson as the build system.

[Eli Schwartz]

This is basically just #670 but from the other direction. When I opened the other ticket, I based it on the assumption that the directions in the tutorial and throughout the documentation -- which say to use #include "doctest.h" -- were correct.

[mitchgrout]

I would support #include <doctest.h> / #include "doctest.h" as the way to properly include the library, as <doctest/doctest.h> personally feels redundant. It also leaves #include <doctest/part> as an obvious choice for include parts of the library if there's ever any splitting of the header into multiple smaller components.