3 ways GTest example
3 ways GTest example

- Updated GTest example tree to lastest project version
- Added conan test_package approach to build the project
- Added step-by-step approach to build the project
- Preserved simple CMake approach to build the project

Signed-off-by: Uilian Ries <d4bad57018205bdda203549c36d3feb0bfe416a7@gmail.com>

conan-io/docs,conan-io/docs,conan-io/docs,conan-io/docs