chore: add more strict types in electron directory

[cino]

• I have read the Contributing Guidelines for this project.
• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for a feature request that matches the one I want to file, without success.

Description of Change

• Added more strict typing to the main files of the electron directory. The ipc-api subdirectory is for a later moment as this is more of another PR.

Motivation and Context

• Convert to typescript #42

Checklist

• My pull request is properly named
• The changes respect the code style of the project (npm run prepare-code)
• npm test passes
• I tested/previewed my changes locally