Remove unused dependencies `eslintConfig` and `sass`

[peterdesmet]

See #253

• package.json still carries an eslintConfig block that is dead: ESLint prefers .eslintrc and never merges the two, so the eslint:recommended and plugin:@typescript-eslint/recommended presets listed there are not actually applied.
• sass and sass-loader are unused - there is no .scss file in the project.