feat: Integrate Jest for JavaScript testing with CI setup

Set up a modern JavaScript testing framework using Jest, integrated with the existing webpack build system. Configure Babel for modern JavaScript support and establish a test file structure and conventions. Update the package.json to include Jest dependencies and scripts for running tests, watching tests, and generating coverage reports. Set up a continuous integration pipeline to run JavaScript tests alongside existing Python tests.

New Features:
- Introduce a modern JavaScript testing framework using Jest, integrated with the existing webpack build system.

Enhancements:
- Configure Babel for modern JavaScript support with a new Babel configuration file.

CI:
- Set up a continuous integration pipeline to run JavaScript tests alongside existing Python tests.

Tests:
- Establish a test file structure and conventions for JavaScript tests, including an example test file to verify the setup.
- Configure test coverage reporting for JavaScript code.

Resolves #27

.gitignore

@@ -1,3 +1,5 @@
+# Jest coverage
+/coverage
 *.py[cod]
 *$py.class
 *.egg-info

babel.config.js

@@ -0,0 +1,9 @@
+module.exports = {
+  presets: [
+    ['@babel/preset-env', {
+      targets: {
+        node: 'current',
+      },
+    }],
+  ],
+};

jest.config.js

@@ -0,0 +1,16 @@
+module.exports = {
+  testEnvironment: 'jsdom',
+  setupFilesAfterEnv: ['<rootDir>/tests/js/setup-tests.js'],
+  moduleNameMapper: {
+    '\\.(css|less|scss|sass)$': '<rootDir>/tests/js/__mocks__/styleMock.js',
+    '\\.(gif|ttf|eot|svg)$': '<rootDir>/tests/js/__mocks__/fileMock.js'
+  },
+  testMatch: [
+    '**/tests/js/**/*.test.js'
+  ],
+  coverageDirectory: 'coverage',
+  collectCoverageFrom: [
+    'private/js/**/*.js',
+    '!**/node_modules/**'
+  ]
+};