test: set up Vitest and add tests for src/index.ts

[hitarth-gg]

Description of Change

• Set up Vitest for testing
• Added mocks for Electron modules
• Added unit tests for src/index.ts
• More tests will be added once this foundational PR for the testing setup is merged

[dsanders11]

@hitarth-gg, did you want to move ahead with updating this PR after #279 was merged? I think it's still a good idea to explore migrating to Vitest, but understand if you want to close this for now and come back to it in the future. 👍

[hitarth-gg]

@dsanders11 I agree, It'd be nice to migrate to Vitest. Last week I actually tried using Vitest in the same way I use Mocha to test things in a real Electron app, but I couldn’t quite figure it out. I’ll need to dig a bit deeper into that.

College schedule is a bit busy this month since I’m preparing for exams, which will likely finish in the last week of September. If needed, we can close this PR for now, or keep it open (whichever is preferred) and I can come back at the beginning of October and continue working on it.

[dsanders11]

@hitarth-gg, thanks for the update. I'll move it to draft state at the moment so it's clear it's still in-progress.