Overlays are not downloaded

[kyleawayan]

When downloading memories using the direct download links in memories_history.json, I have found that most videos (looks like the newer ones that use HEVC) do not include the overlays (captions, clock overlay, etc.).

Downloading the actual memories from the request data form using the "Include your Memories and other saved Media" checkbox looks like it includes overlays too... However, the overlays are in separate transparent .png files than the actual media.

Will most likely make a PR to somehow combine the JSON and the actual memories, using ffmpeg to composite the overlays with the actual media. The JSON will be required because the "Include your Memories and other saved Media" dataset omits the exact time and location metadata.