Features

• Compat: Add flushSync (#3094, thanks @zephraph)

Bug Fixes

• Prevent eager child removal (#3210, thanks @JoviDeCroock)
• Compat: Update Fake React Version (#3189, thanks @tim-on-github)
• Fix react-spring error caused by augmented function contexts (#3165, thanks @developit)
• Use Array.prototype.slice.call for children arguments (#3143, thanks @fzzle)
• Improve performance of vnodeId generation (#2978, thanks @developit)
• Fix: should override children if null is provided as an argument (#3091, thanks @clyfish)

Size

• refactor(diff-index): reuse i to reduce size (-32b) (#3193, thanks @liuarui)
• Simplify unmount logic (#3120, thanks @andrewiggins)

Typings

• Fix type definitions (#3191, thanks @craftedsystems)
• Fix undefined initializer case for useState type (#3185, thanks @rschristian)
• Make typings deno compatible (#3079, thanks @lucacasonato)
• Change typing of event.this to be never (#3147, thanks @JoviDeCroock)
• Update signature of lazy to reflect behavior (#3139, thanks @JonasKruckenberg)
• Improve typing of forwardRef (#3144, thanks @cmlenz)
• Fix the useRef typing to include undefined when called without initial value (#3056, thanks @cmlenz)

Maintenance

• Docs: Removing suggestion to install Preact CLI (#3204, thanks @rschristian)
• Upgrade karma-esbuild to support M1 chips (#3153, thanks @marvinhagemeister)
• Rely directly on performance.now (#3130, thanks @developit)
• Add The Guardian as a Github backer (#3086, thanks @mchv)
• Fix typo in issue template (#3067, thanks @rschristian)