Incorporate type checking

What problem do you want to solve?

The project includes TypeScript type declarations, but types are not used in the code to catch applicable errors.

What is the proposed solution?

Add JSDoc-based types to the codebase to improve type checking and catch errors early. This should be done at least for production code, and as appropriate for test code. Use the default tsconfig.json from config-files. Also add the appropriate CI job templates.