Index all files in model directory

[ksuquix]

They don't necessarily need thumbnailed or anything, but probably a notes field (when that gets implemented). Most importantly, on the model page, you should have a list of links for all the files in that folder for download. (READMEs, license documentation, cura/lychee files, etc, etc)

[Floppy]

Also requested by @lloydpick in #1736:

I have quite a few models that include pdf assembly instructions or BOM lists and the same goes for assembly videos. I've stored these along side the 3d models, however it appears manyfold has no way of showing these back to the user. I'm not looking for an embedded player or viewer, but perhaps extra links on the right navigation to simply download them?

[Floppy]

@slitzer in #1377 says:

Is there a way to specify what file types are displayed in the viewer?

The problem im trying to solve is some folders have a few files and thats fine - when there are over 20 or so files in a collection this becomes a pain to manaully download each file. I know there is a request to add a d/l button, however I imagine this will be problematic when dealing with large files (and trying to zip them all would take a while, most likely timeout

Instead could we can a fiilter to choose what gets detected, and able to be downloaded (similar to LYS files) this way I could add a .zip or .7z file to this and have the option to download the zip file (which would be all files in 1 download)