Possibility of migrating to CMake and GoogleTest

[wdhongtw]

As Virgil already addressed in README, it's good to use GoogleTest and CMake.

I have a working example here https://github.com/wdhongtw/JSLikePromise/tree/feat-gtest .
One commit for migrate the testing framework to GoogleTest, and another for using CMake to do build automation / generation.

There are still some parts that not look good.

• The test case/suite need to be prefix by All/Any/Valued..., since that the macro for GoogleTest seems to not support same name in different C++ namespace.
• Trying to keep indentations and minimize the line of changes, but anonymous namespaces are introduced in test files.
• The main target, the header-only library itself is not represented as a project in generated VS solution file.
• GoogleTest is included by CMake FetchContent, so there is two 3rd target gtest and gtest_main in the generated solution file.

If this looks appealing, maybe I can submit PR and/or discuss how can we enhance this. :D