fix: Implemented $thumbsDirectory initialization.

Oleh Polishchukrequested to merge
issue/video_embed_html5-3586425:3586425-module-saves-thumbnails into 2.0.x

fix: Module saves thumbnails in /wed/:/video_thumbnails folder instead of /web/sites/default/files/video_thumbnails

Implemented $thumbsDirectory initialization

Closes #3586425

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