Add errata for fix to marginStart/End for row-reverse flex direction (#1419)

Summary:
Pull Request resolved: https://github.com/facebook/yoga/pull/1419

X-link: https://github.com/facebook/litho/pull/961

X-link: https://github.com/facebook/react-native/pull/40803

This stack is ultimately aiming to solve https://github.com/facebook/yoga/issues/1208

This adds an value to the Errata enum. I will use this to gate this fix as there is potential for users to rely on this bug or have a hack in place to fix it and this would be a breaking change.

Reviewed By: NickGerleman

Differential Revision: D50145273

fbshipit-source-id: 913d2103cd31c1fa94cb39fc15d05b0c0b255920

enums.py

@@ -67,6 +67,8 @@ ENUMS = {
         # Allows main-axis flex basis to be stretched without flexGrow being
         # set (previously referred to as "UseLegacyStretchBehaviour")
         ("StretchFlexBasis", 1 << 0),
+        # Solely uses the flex-direction to determine starting and ending edges
+        ("StartingEndingEdgeFromFlexDirection", 1 << 1),
         # Enable all incorrect behavior (preserve compatibility)
         ("All", 0x7FFFFFFF),
         # Enable all errata except for "StretchFlexBasis" (Defaults behavior