Migrate component tests to Jest and React Testing Library

[webinista]

• test/components/Button.unit.test.jsx
• test/components/CloseButton.unit.test.jsx
• test/components/ColorInput.unit.test.jsx
• test/components/ColorSwatch.unit.test.jsx
• test/components/Controls.unit.test.jsx
• test/components/Modal.unit.test.jsx
• test/components/ModalTrigger.unit.test.jsx
• test/components/SelectOption.unit.test.jsx
• test/components/TextInput.unit.test.jsx

Related to #110, #18

[webinista]

Need to understand when to introduce React Testing Library.

Docs and Tutorials:

• https://reactjs.org/docs/testing.html
• https://jestjs.io/docs/tutorial-react
• https://www.freecodecamp.org/news/8-simple-steps-to-start-testing-react-apps-using-react-testing-library-and-jest/
• https://blog.logrocket.com/testing-apps-with-jest-and-react-testing-library/
• https://www.robinwieruch.de/react-connected-component-test/