Add a todo

[cartooncatfish]

After adding the follows

AddTodo.propTypes = {
  submitTodo: PropTypes.func.isRequired,
};

Got an error:

 PASS  src/components/addTodo/test.js
  ● Console

    console.error node_modules/prop-types/checkPropTypes.js:19
      Warning: Failed prop type: The prop `submitTodo` is marked as required in `AddTodo`, but its value is `undefined`.
          in AddTodo (at test.js:10)

 PASS  src/App.test.js
  ● Console

    console.error node_modules/prop-types/checkPropTypes.js:19
      Warning: Failed prop type: The prop `submitTodo` is marked as required in `AddTodo`, but its value is `undefined`.
          in AddTodo (at App.js:7)
          in App (at App.test.js:9)

Test Suites: 2 passed, 2 total
Tests:       6 passed, 6 total
Snapshots:   0 total
Time:        1.097s, estimated 2s
Ran all test suites related to changed files.

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