add cmake support

[madmongo1]

Includes installer which creates a namespaced export

Usage:

cmake_minimum_required(VERSION 3.16)

project(cppcoro-check)

find_package(cppcoro REQUIRED)

add_executable(check main.cpp)
target_link_libraries(check cppcoro::cppcoro)

Tested on fedora-33 linux with clang-11 -std=c++20 -stdlib=libc++

[Garcia6l20]

Hi,
there is already a PR for this co_awaiting for review here.

If you want to make suggestions/contribution to it I would suggest you to PR directly on andreasbuhr branch. This branch integrates contributions many from people, tested on msvc, clang and gcc.

[madmongo1]

OK, great that it's already in progress.
I had written this cmake script so that I could test the library and felt it was polite to offer it back upstream.