yc/add matrix demo - Adding a server example for MATRIX Creator/Voice boards

[yoelrc88]

• added configuration files ready for this example
• added small guide on how to install/run the demo
• added a gif as a reference of what the demo does

[FrancoisGrondin]

Thank you for this code! I see you are using json-c to parse from JSON. I try to avoid using external libraries as much as possible and so yesterday I just wrote a json parser to integrate directly in odas. As soon as I have push this in a dev branch, I'll look how I can merge your code to odas.

[yoelrc88]

Oh great! As soon as you push that json code I will update this example.
Thank you

[FrancoisGrondin]

Here is the code for the homemade JSON parser. I'm still working on the server side implementation... I'll merge to master when I'm done and I clean a bit, but you can already have an idea of the way the json parser works here: https://github.com/introlab/odas/blob/dev/src/odas/utils/json.c