replace experimentalObjectRestSpread with ecmaVersion: 2018
replace experimentalObjectRestSpread with ecmaVersion: 2018

https://github.com/tc39/proposal-object-rest-spread has become a part
of the ECMAScript standard as of version 2018 (also known as ECMAScript
9).

experimentalObjectRestSpread will be removed in the future from eslint.

LLK/eslint-config-scratch,LLK/eslint-config-scratch