feat: extend indexer ethscription creation support for additional content types

[Snepsid]

This pull request expands the detection logic for supported ethscription content types in the EthscriptionsService. The change makes it possible to recognize a wider variety of content types beyond the previously supported image formats.

Content type support enhancements:

• Updated the check for possible ethscription creation to include additional content types such as JPEG, JPG, WEBP, AVIF images, WEBM videos, HTML, JSON, and PDF (both with and without charset specifications), in addition to the previously supported SVG, PNG, and GIF formats.