Display file names on Images page UI

[judge2020]

Is your feature request related to a problem? Please describe.
File names are currently searchable (via #206), however, nowhere in the Philomena frontend is the file name of the image visible. Currently it is only visible in API responses.

Describe the solution you'd like
Potentially an area of the image page displays the file name.

Describe alternatives you've considered
Potential alternatives that could be less intrusive:

• alt text on the image itself is the file name
• a expanding view of the API response (potentially only if the account has some sort of developer mode or advanced mode enabled)

Additional context
Potential issues:

1. file names could have explicit or vulgar content not in-line with the image tags / ratings of the image, eg. see this image
2. File names pulled from URLs are after the last / in the URI, and include the query params. E.g. the image linked above has signature query params from Discord's signed image URL thing that ensures you can't permanently hotlink an image.

[judge2020]

Another potential improvement related to this could be to deliver images downloaded via the "FS" button with the file name via the Content-Disposition: filename= param, however, the second issue I presented is also applicable with this. Don't want to make an issue for that since I feel like it's a lot less likely, especially since image downloads are handled by a CDN in prod, not the app.

[mdashlw]

It's easy to make a user script for this (I have one here).

If it comes to Philomena, I think it'd be in the same place in UI behind an opt-in user setting.

I don't like the idea of incorporating it somewhere proper, like in download filenames or as alt text. It should only be treated as an artifact of the original upload file, not an essential property of our Image model.