v0.0.2

how to process c++ third-party dependency and do unittest

• use FetchContent command to download and then add_subdirectory third-party library
• use googletest to do unit test

v0.0.1 simplest cpp library

• the simplest cpp library with cmake build
• the core knowledge include：
  1 namespace
  2 function,
  3 class
  4 the seperation of header and source file
  5 how to use cmake build a library which is organised into multiple folders and sub-projects