refactor: use type-checked JS instead of TS for quickstart examples

[JKRhb]

This PR contains an initial proposal for a partial implementation of #1108, removing the (sort of redundant) TS files for the quickstart examples and instead adding type checking via a @ts-check comment to the respective JS example files. Additional type information is added via JSDoc comments.

This PR can serve as a basis for discussing if this is the direction we want to go with the other examples as well – if so, then I would open PRs for the other examples (or rather: those that should remain in the node-wot repository) as well.