React 16.13.0 release notes

Warn when a string ref is used in a manner that's not amenable to a future codemod (@lunaruan in #17864)
Deprecate React.createFactory() (@trueadm in #17878)

Warn when changes in style may cause an unexpected collision (@sophiebits in #14181, #18002)
Warn when a function component is updated during another component's render phase (@acdlite in #17099)
Deprecate unstable_createPortal (@trueadm in #17880)
Fix onMouseEnter being fired on disabled buttons (@AlfredoGJ in #17675)
Call shouldComponentUpdate twice when developing in StrictMode (@bvaughn in #17942)
Add version property to ReactDOM (@ealush in #15780)
Don't call toString() of dangerouslySetInnerHTML (@sebmarkbage in #17773)
Show component stacks in more warnings (@gaearon in #17922, #17586)

Warn for problematic usages of ReactDOM.createRoot() (@trueadm in #17937)
Remove ReactDOM.createRoot() callback params and added warnings on usage (@bvaughn in #17916)
Don't group Idle/Offscreen work with other work (@sebmarkbage in #17456)
Adjust SuspenseList CPU bound heuristic (@sebmarkbage in #17455)
Add missing event plugin priorities (@trueadm in #17914)
Fix isPending only being true when transitioning from inside an input event (@acdlite in #17382)
Fix React.memo components dropping updates when interrupted by a higher priority update (@acdlite in #18091)
Don't warn when suspending at the wrong priority (@gaearon in #17971)
Fix a bug with rebasing updates (@acdlite and @sebmarkbage in #17560, #17510, #17483, #17480)