Support ESLint 7.x

Created by: MichaelDeBoey

ESLint v7.0.0 is released 🎉

devDependencies should be compatible with ESLint 7 too before we can merge this one:

• eslint-plugin-flowtype (https://github.com/gajus/eslint-plugin-flowtype/issues/446)
  • https://github.com/gajus/eslint-plugin-flowtype/pull/447
  • Release
• eslint-plugin-import (https://github.com/benmosher/eslint-plugin-import/issues/1772)
  • https://github.com/benmosher/eslint-plugin-import/pull/1715
  • https://github.com/benmosher/eslint-plugin-import/commit/6a110dd16a7fd775f08601054bf14ffd503eea7b
  • Release
• eslint-plugin-jsx-a11y (https://github.com/evcohen/eslint-plugin-jsx-a11y/issues/683)
  • https://github.com/evcohen/eslint-plugin-jsx-a11y/pull/684
  • Release
• eslint-plugin-react
  • https://github.com/yannickcr/eslint-plugin-react/pull/2635
  • Release
• eslint-plugin-react-hooks (https://github.com/facebook/react/issues/18876)
  • https://github.com/facebook/react/pull/18878
  • https://github.com/facebook/react/pull/18897
  • Release

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BREAKING CHANGE: Requires Node@^10.12.x || 12.x BREAKING CHANGE: Requires ESLint@^7.x

Closes #8977 (closed)