Add CMake support for static lib

[valbok]

[kimvnhung]

Hope you to finish this issue soon, I expect to use this QtAVPlayer like a library in a CMake project

[valbok]

Hope you to finish this issue soon, I expect to use this QtAVPlayer like a library in a CMake project

Thanks for the interest! First version of QtAVPlayer was implemented as a library and after that decided to bundle the lib directly to the user's project.

So will add QtAVPlayer.cmake to be included to the project manually.

[valbok]

https://github.com/valbok/QtAVPlayer/pull/473/