refactor(w3c/level): improve method docs

[marcoscaceres]

No description provided.

[sidvishnoi]

I'm not finding the benefit of this particular class of refactor. How does typescript help here?

[marcoscaceres]

The LocalizationStrings helps remind us to add all the supported languages. So, although it's not super useful here, it's going to be useful in other places where we have localization language gaps.

[sidvishnoi]

I'm in favor of grouping all these PRs into bigger chunks.

Nits to be followed:

1. Make this comment appear in one line.

   - /**
   - * @type {LocalizationStrings}
   - */
   + /** @type {LocalizationStrings} */

2. Remove this "Localization data based on the user's language preference." comment as it's noisy.