Collections are packages of their own

A collection is no longer a file inside a mod: it is a package (folder or zip)
named after its id with collection.json, cover and optional locale/, shipped in
collections/ next to the mods or kept by the player in user://collections/.
Covers and texts come from the package; mods do not ship collections.

collections/frontend.json

@@ -1,33 +0,0 @@
-{
-  "id": "frontend",
-  "kind": "frontend",
-  "name": "Front-end",
-  "author": "ct",
-  "version": "1.0.0",
-  "description": "Loaded with every game and on its own without one: the main menu, settings, save browser and the mod manager.",
-  "locale": [
-    { "lang": "ru", "name": "Оболочка", "description": "Загружается с каждой игрой и без неё: главное меню, настройки, сохранения и менеджер модов." }
-  ],
-  "mechanics": [
-    {
-      "id": "menu",
-      "name": "Main menu",
-      "role": "ui",
-      "description": "Main menu, settings and the save/load panels.",
-      "locale": [
-        { "lang": "ru", "name": "Главное меню", "description": "Главное меню, настройки и панели сохранения/загрузки." }
-      ],
-      "mods": ["menu_base>=1", "ui_base>=1", "audio_base>=1"]
-    },
-    {
-      "id": "mods",
-      "name": "Mod manager",
-      "role": "tools",
-      "description": "Catalog, installation and the game constructor.",
-      "locale": [
-        { "lang": "ru", "name": "Менеджер модов", "description": "Каталог, установка и конструктор игр." }
-      ],
-      "mods": ["mod_manager>=1"]
-    }
-  ]
-}