chore: update major versions of dev deps

[kaitmore]

summary of updates

• commitlint (no relevant changes)
  • see changelog https://github.com/conventional-changelog/commitlint/blob/master/%40commitlint/config-conventional/CHANGELOG.md
• eslint
  • ran formatter
  • removed prettier config from .eslintrc https://github.com/prettier/eslint-plugin-prettier#options

    Note: While it is possible to pass options to Prettier via your ESLint configuration file, it is not recommended because editor extensions such as prettier-atom and prettier-vscode will read .prettierrc, but won't read settings from ESLint, which can lead to an inconsistent experience.

• webpack
  • use --mode=production refactor: remove --dev and --prod flags webpack/webpack-cli#1693
  • not compatible with node 8 (carbon), update from node:carbon in CI to node:14 like the dashboard
• autoprefixer
  • requires postcss/postcss-leader peerdep Error: [object Object] is not a PostCSS plugin postcss/autoprefixer#1358 (comment)

test checklist

• npm run start
• npm run build
• npm run test
• npm run pack - test build in dashboard