Integrate Karma Infrastructure

[rajsite]

Pull Request

🤨 Rationale

Introduces karma test infrastructure for writing unit tests. Modeled after the integration in fast foundation.

This does not integrate the playwright-based FAST e2e testing framework.

👩‍💻 Implementation

Migrated a similar karma configuration as used in FAST with some differences:

• Using jasmine for the BDD framework instead of mocha to match Web Chapter recommendations
• Switched to Webpack 5 to align with storybook and Angular integrations. Fast is using Webpack 4 but has been working on migrating to Webpack 5.
• Does not integrate Fast's approach to code coverage due to lack of webpack 5 support in one of the istanbul plugins.

Some other minor refactors included in this change:

• Created an eslint config at the root to lint config js files for karma, storybook, etc. Currently disabled for storybook to address in a follow-up.
• Enabled the importsNotUsedAsValues TypeScript compiler rule for nimble components. This is helpful as nimble components currently relies on side-effects of imports and as a result of enabling the rule it becomes explicit when an import is done for side-effects instead of just for type imports, ie import './someFile'; (note how there are no named imports, just side-effects).

🧪 Testing

Included a sample test file for the Button based on existing FastFoundation tests. Does not represent what the Button tests should cover but is just used as an example to test the infrastructure. In a follow-up the example tests should be replaced with tests for Nimble Button specific features (currently just appearance configuration).

✅ Checklist

• I have updated the project documentation to reflect my changes or determined no changes are needed.

[rajsite]

@jattasNI resetting you as there was some big folder structure changes and to check the fixture docs