[Feature] Add ability to stream play video and audio files and image previews

It would be nice if media files that are being downloaded could play with in-built player.

Almost every cloud storage provides ability to range download, so there's not a big problem.
And as I committed in another request, please add optional setting to enable creating encrypted image/video previews for media file uploads.

I suggest that every media file that is being uploaded should contain preview block (encrypted of course) in the start of content, and if possible it should be with user's predefined quality settings.

When user opens a folder containing media files for the first time, on PC or Android, Cryptomator starts to download predetermined media files, when it gets to the end part of block containing thumbnail - it stops, shows thumbnail of file, saves preview in local cache for faster user experience.

If user wants to download a media file, Cryptomator just ignores/deletes thumbnail block and saves original file.

With these abilities Cryptomator would be perfect and user-friendly.
Cheers!! ❤️🏆🥇🧠

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