[Feature Request] Add fallback for media not found in memories_history.json to use date found in media filename

[gabeklavans]

I did a full export with everything checked, then I unfortunately started deleting my memories from snapchat before I realized while reading this repo's README that I had to do another export to get the memories_history.json RIP my metadata for those ~100 pictures but I'd at least like to utilize the work done in this project to combine the overlays onto the media for those pictures.

BTW what a user-hostile system of exporting snapchat has created... like c'mon. I'm glad it exists at all at least.

[gabeklavans]

Actually, now that I'm thinking about it, the day is encoded in the filename of all the exported media. Maybe this feature request is actually to implement a fallback for any media in the input folder that isn't found in the memories_history.json to use the day stored in the filename. That would at least get the day right (+/- 1 day cuz timezones) and that's good enough for me tbh.