[docs] Add features and logo to publiccode.yml

[libremente]

Hi @cappe87,

since the publiccode.yml file does not pass the validation tests required by our crawler I made the following modifications:

• inserted the logo locally (in the root of the repo)
• inserted some features (it's a mandatory key).

Since I am not sure whether you can (or want to) insert an SVG in the root folder I tried to do so, however please note that the publiccode.yml standard mandates the images to be stored inside the repository (see this for reference), so if you don't store the image file inside the repo you should also remove the logo key from the publiccode.yml.
Please feel free to change the features key, I've inserted some placeholder just to make the test pass but they might not be very accurate.

Feel free to ping me in case you need help on this. Thanks a bunch!

[cappe87]

Thank you @libremente

[nemesifier]

Thank you @cappe87 and @libremente! 👍