[1] Remove the context menu feature (domenic著, ) <https://github.com/whatwg/html/commit/e7e8c88ecdd7cdc96171f05ab6fe23b56dd48d8a>
[2] Remove "onhide" from obsolete attributes (a1626著, ) <https://github.com/whatwg/html/commit/361207c9ab4555de7ba21cdd1181d7cea116c2a8>
[3] Remove "onhide" from obsolete attributes · Issue #2860 · whatwg/html () <https://github.com/whatwg/html/issues/2860>
[4] Fixing #2860 (Remove "onhide" from obsolete attributes) by a1626 · Pull Request #2976 · whatwg/html () <https://github.com/whatwg/html/pull/2976>