* [Reporting] Screenshot Service RFC
* rewrite summary
* simplify design
* Update 0009_screenshot_mode_service.md
* mention the 3 screenshot report apps
* try not to say this is a high-level service
* clarify that print media css is just ok
* clarify the intent
* drop the `app`
* add the possibility to test screenshot mode through a URL parameter
* keep it more low-level
* keep the discussion high level
* move a sectioin of text
