Add an example CMakeLists.txt for building projects and add it to documentation

[hkashyap]

We need to add an example CMakeLists.txt for the projects, say for hello_world, and explain in the docs how to use it for building the project and the arguments to cmake.

[hkashyap]

@mode89 can you please help us with this?

[mode89]

Hi @hkashyap. Sure, I'll do it the next week.