Write an article about JSS internal mechanics

Will do it if enough people are interested, please leave a reaction and/or other questions to clarify.

- How we do we generate CSS rules
- How do we render the rules to CSSOM and style to the DOM
- How do we update
- How do we remove
- Why are function values in JSS so fast, faster than inline styles in react

More questions on [twitter](https://twitter.com/oleg008/status/852551945403457539)

Start by reviewing JSS's internal mechanics against the questions listed in the issue: CSS rule generation, CSSOM and DOM rendering, updates, removals, and function-value performance. The work is done when these topics are covered in a coherent article, but the issue does not name source files, tests, or a documentation location.

Written by the indexing model from the issue text.