Feature request: custom download folder

[NotaInutilis]

Problem
Currently, all custom download entries are stored in one json file which every custom update package is fighting for: unless the user is careful, it is very likely to be overwritten. Updating an AIO package or copying the config file from a patch will delete handwritten or imported entries for all other mods that use AIO updater. There is no merge, only rewrite.

Proposed solution
Parse json files from a custom download folder. Each json can have a unique name, e.g. AIO.json, patch.json... in order to prevent overwrites.