Add ImageAssets for download (#932)

* Add ImageAssets for download
* Update directory for consistency with video assets directory and add soccer image
* Fix unaligned table
* Add support for `ImageAssets` and extend `download_assets` functionality to handle both image and video assets.
* Refactor `Assets` enum initialization and improve `download_assets` logic with enhanced file checks and re-download handling. Add new tests for invalid asset cases and update existing test assertions.
* Simplify `download_assets` type handling and refactor `Assets` enum with additional attributes for filename and md5_hash.

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: jirka <6035284+Borda@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>