Adding Readme files with links to images in section

[DinisCruz]

This will make it easier to see what is currently in the files

[jmarcil]

Hello Dinis,

thank you for submitting those changes.

However I'm afraid I cannot accept the current PR to be merged.

Here's why:

• Currently the img src are pointing directly to your repo filetrust, meaning that whatever version is in your master branch will be shown on this project page. I'm afraid this is not acceptable and relative paths would be the solution.
• We actually need an index per example rather than per type of model. By that I mean that for example iot-device has an attack tree and a flow diagram, and we should have some sort of index grouping it together.

Overall I'd like also to apologize that the Contribute section of the main README isn't finished yet (#4), but at this point we are more welcoming of PRs with examples contributions rather than structural suggestions on how to present the project.

I will however take in account what you where trying to achieve here, and try to make up an index that has some visual elements that people can quickly see. To be addressed in #26.

Thanks!