[TASK-1046] Add unit test for component

[pauloamorimbr]

Checklist

1. If you've added code that should be tested, add tests
2. If you've changed APIs, update (or create!) the documentation
3. Ensure the tests pass
4. Make sure that your code lints and that you've followed our coding style
5. Write a title and, if necessary, a description of your work suitable for publishing in our release notes
6. Mention any related issues in this repository (as #ISSUE) and in other repositories (as kobotoolbox/other#ISSUE)
7. Open an issue in the docs if there are UI/UX changes

Description

This commit creates the base configuration and samples for adding unit tests with Jest.
Simple tests were created for the Button and KoboSelect3 components as samples.

Notes

• Some new packages were added for jest to work
• Configuration for jest was added into /jsapp/jest
• 2 new scripts were created on package.json:
  • npm run jest
  • npm run jest-watch (Very useful when writing tests)
  • Both scripts can filter test files as in: npm run jest-watch -- Button
• To avoid confusion with mocha .tests.* file, we're using the .spec.* extension for tests.
• A test for the Button component was added checking for its interaction when enabled and disabled
• A test for the KoboSelect3 component was added checking for its mouse and keyboard interaction

[notion-workspace]

🏍️ UI Component Unit Tests, e.g. Data Table