Add a provider logo URL snippet to the image utility docs

[TDanks2000]

Background

Watch provider responses include logo_path, and the package exposes getFullImagePath, TMDB_IMAGE_BASE_URL, and ImageSizes. The image utility docs currently focus on movie posters and image endpoint results.

Proposed Change

Add a short snippet showing how to convert a watch provider logo_path into a usable image URL.

Acceptance Criteria

• The snippet uses tmdb.movies.watchProviders(...) or tmdb.watchProviders.movie().
• The snippet handles missing logo_path safely.
• The snippet uses existing image helpers rather than hard-coded URL concatenation.
• No unsupported watch provider behavior is claimed.

Files Likely Involved

• docs/image-utilities.md
• docs/endpoints/watch-providers.md