[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 <git@sophiebits.com>

beta/src/sidebarLearn.json

@@ -162,6 +162,10 @@
             {
               "title": "Manipulating the DOM with Refs",
               "path": "/learn/manipulating-the-dom-with-refs"
+            },
+            {
+              "title": "Synchronizing with Effects",
+              "path": "/learn/synchronizing-with-effects"
             }
           ]
         }