Add CMake configuration for ESP-IDF component

[omrawaley]

Hi, amazing job! This library is incredible and super easy to use after a few tweaks.

In order to use this library as a component with the ESP-IDF, I had to add a small CMakeLists.txt. With the current branch, I got a build error complaining about it missing since all IDF components need one.

After adding this file, I was able to add the Jet library to my idf_component.yml like this:

dependencies:
  jet:
    git: https://github.com/CubeCoders/Jet.git

I'm not sure if the absence of the CMakeLists.txt was intentional so that multiple platforms could be targeted but, in any case, it would be worth adding it somewhere (maybe in a new branch) since the current ESP-IDF component is technically non-functional.

Thanks!