JSX not allowed in files with extension ‘.tsx’eslint(react/jsx-filename-extension)

You probably want to configure the react/jsx-filename-extension rule in your .eslintrc.js so that ESLint is happy about JSX inside your TypeScript files:

rules:  {
  'react/jsx-filename-extension': [2, { 'extensions': ['.js', '.jsx', '.ts', '.tsx'] }],
},