Support Cmake as a build system

[masatake]

This is mostly based on @ParticleG's work. See #51.

[masatake]

@ParticleG You wrote in #51:

I'm coding on Windows and use vcpkg to manage CMake packages.

I would like to know more about this.
Do you mean you will use libreadtags with vcpkg when I merge this pull request? If so, I want to test this use case on GitHub actions (or Appveryor?).

[masatake]

This step is for the source code cloned from the git repository.

[ParticleG]

@ParticleG You wrote in #51:

I'm coding on Windows and use vcpkg to manage CMake packages.

I would like to know more about this. Do you mean you will use libreadtags with vcpkg when I merge this pull request? If so, I want to test this use case on GitHub actions (or Appveryor?).

Hmmm, currently I wrote a custom fetch_libreadtags.cmake, which is using my forked repo, the logic is exactly the same as I mentioned in README.md:

include(FetchContent)

if (EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/cmake/libreadtags-master.zip")
    FetchContent_Declare(
            libreadtags
            URL file://${CMAKE_CURRENT_SOURCE_DIR}/cmake/libreadtags-master.zip
    )
else ()
    FetchContent_Declare(
            libreadtags
            GIT_REPOSITORY https://github.com/ParticleG/libreadtags.git
            GIT_TAG master
    )
endif ()

FetchContent_MakeAvailable(libreadtags)

If you want to use this IN vcpkg (which is a C++ CMake based dependency manager by Microsoft), you need to create a PR in their repo and add some more stuff like manifest (Yes, it's Git-based version controll)

[ParticleG]

Also CMake come along with a testing tool called CTest. I'm not sure if you'd like to use it, I just pasted the link to the official documentation here

[masatake]

@ParticleG thank you for the information.

I'm interested in registering libreadtags to vckg. However, I cannot put it as a high-priority item in my queue.

Using CTest is more interesting. Anyway, I will merge this.

[masatake]

@ParticleG, thank you very much.

I'm thinking about releasing a new version.

[ParticleG]

@ParticleG thank you for the information.

I'm interested in registering libreadtags to vckg. However, I cannot put it as a high-priority item in my queue.

Using CTest is more interesting. Anyway, I will merge this.

I can try making a port and create a PR to vcpkg, if you want. But I'm quite busy this month, so this could go slowly