tools: enable no-unsafe-optional-chaining lint rule

This rule is new in ESLint 7.15.0.

PR-URL: #36411
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>

.eslintrc.js

@@ -239,6 +239,7 @@ module.exports = {
     'no-unreachable': 'error',
     'no-unsafe-finally': 'error',
     'no-unsafe-negation': 'error',
+    'no-unsafe-optional-chaining': 'error',
     'no-unused-expressions': ['error', { allowShortCircuit: true }],
     'no-unused-labels': 'error',
     'no-unused-vars': ['error', { args: 'none', caughtErrors: 'all' }],