v18.0.0
Add aspectRatio to the unitless list (#21100)
Don't use nested objects to "namespace" namespace constants (#21073)
Add custom element property support behind a flag (#22184)
Drop the year from Facebook copyright headers and the LICENSE file. (#13593)
Remove the deprecated React Flare event system (#19520)
Remove redundant initial of hasOwnProperty (#21134)
Use console directly instead of warning() modules (#17599)
Remove the Fundamental internals (#20745)
[RFC] Codemod invariant -> throw new Error (#22435)
Improve DEV errors if string coercion throws (Temporal.*, Symbol, etc.) (#22064)
Clarifications
Add `imageSizes` and `imageSrcSet` to know props (#22550)
Add aria-description to the list of known ARIA attributes (#22142)