[Beta] Synchronizing with Effects (#4742)

* [WIP] Effects

* More

* More

* Typo

* More

* tweaks

* typo

* note

* Add playsinline

* Fix

* Typo

* Oops

* More content

* Compress a bit

* edits

* oops

* Tweaks

* tweak

* Inline the deep dive

* fix

* typos

* add deep dive

* oops

* Clarify

* Add third case

* oops

* edit

* [beta][effects] Reword effects-in-render counterexample (#4722)

* reframe

* oops

* ok

* edits

* fix

* remove special styling

* tweak

* oops

* tweak

* challenges

* tweaks

Co-authored-by: Sophie Alpert <[email protected]>

Author: gaearon