feat: add documentation into README.md

[gioboa]

Changes

This PR add documentation section inside README.md file

Fixes #19

Checklist

• [x] My changes generate no new warnings

[gioboa]

@getify What do you think about this first draft? Can I go on with the encryption logic section?

[gioboa]

This is the first version of the documentation part.

[detronetdip]

@gioboa what's about creating a static webpage for the whole documentation which will be deployed using github pages and can be addressed from README.

[gioboa]

@detronetdip sounds good. After merging this first part of the documentation I think can be a nice thing to do. I usually proceed step by step to get always a stable situation

[getify]

I would actually prefer we move this documentation into a separate markdown file (call it "specs.md" maybe?) so we reduce the noise of churn on it compared to the README... in fact, perhaps some of the "For Developers" section could actually move out of the README and into that new doc.

[detronetdip]

@getify that's also a good idea.

[gioboa]

@getify Here you are 🚀 I moved documentation section into SPECS.md file

[getify]

LGTM as a first pass!