chore: Set up automated testing framework for the extension

[dineshsutihar]

Is your feature request related to a problem?

As the extension grows and more people contribute, the risk of accidentally breaking an existing feature (a "regression") increases. We currently rely on manual testing, which is time-consuming and can miss things.

Describe the solution you'd like

1. Integrate a testing framework like Jest or Vitest into the project.

2. Write a few initial unit tests for simple, pure functions (e.g., the utility functions in cache.js are a good place to start).

3. Create a new GitHub Action workflow that automatically runs the test suite on every pull request made to the develop and main branches. The PR should be blocked from merging if the tests fail.

Additional context

This is a foundational task for ensuring the long-term stability and quality of the project. It gives contributors confidence that their changes don't have unintended side effects and makes the review process much easier.

[singhxabhijeet]

Hey @dineshsutihar, can I work on this?

[dineshsutihar]

@singhxabhijeet I have assigned it to you.