Let manifest sources be declared in JSON

[cheapmanga]

As discussed — the JSON half only. No plugin loader, no dll, nothing loaded.

A .json file under %AppData%\LuaToolsGui\sources\ declares extra manifest sources. They appear as rows on the Add page and install through the existing pipeline.

{
  "schema": 1,
  "name": "Example sources",
  "sources": [{
    "name": "example-zip",
    "displayName": "Example",
    "kind": "manifestZip",
    "url": "https://raw.githubusercontent.com/someone/some-repo/main/{appid}.zip",
    "badge": "Free"
  }]
}

Why: the sources the app can fetch from are fixed at build time, so following a repo that moved means cutting a release. This makes it a line of JSON.

A file can only say where manifests come from. It names one of two shapes the app already consumes — manifestZip (<appid>.zip) or luaFile (<appid>.lua) — and the app does the fetching. There is no way for one to supply code, a binary, or a routine of its own, so installing one from a stranger cannot execute anything.

Three choices worth flagging for review:

• Rows are appended after the app's own sources rather than ranked among them. That order is yours to decide, not a dropped-in file's.
• They're exempt from the lua.tools sign-in gate, since they're fetched from the url the file names and never touch lua.tools.
• The availability probe goes through GithubProxy like the download does — one that skipped it would report "doesn't have the game" whenever GitHub was blocked, while the download would have gone through a mirror. Hosts that refuse HEAD get a one-byte ranged GET.

Refusals (a name already in use, non-https, missing {appid}, unknown kind) are listed in Settings → Manifest sources with the reason; one bad entry doesn't take a file's good ones with it. Files are re-read when that page opens, so no restart.

All 29 languages. Format documented in SOURCES.md. Happy to change any of it, or drop it if you'd rather not have the surface.

[madoiscool]

cool, will merge after dealing with conflits