fix forwarder icon passing in the wrong size, fix github zip detection / extraction, add back url in json

- i was passing the wrong size for icon, so it always failed to load.
- i didnt realise zips can have many content types, so now i search for the name "zip" which works well.
- extracting a zip will fail if the files are all in the root, ie, no folder, and the subfolders do
  not already exist.
- fix misspelling of download.

assets/romfs/github/ftpsrv.json

@@ -1,12 +1,8 @@
 {
-    "owner": "ITotalJustice",
-    "repo": "ftpsrv",
+    "url": "https://github.com/ITotalJustice/ftpsrv",
     "assets": [
         {
-            "name": "switch_application.zip"
-        },
-        {
-            "name": "switch_sysmod.zip"
+            "name": "switch"
         }
     ]
 }

assets/romfs/github/sphaira.json

@@ -1,4 +1,3 @@
 {
-    "owner": "ITotalJustice",
-    "repo": "sphaira"
+    "url": "https://github.com/ITotalJustice/sphaira"
 }

assets/romfs/github/untitled.json

@@ -1,4 +1,3 @@
 {
-    "owner": "ITotalJustice",
-    "repo": "untitled"
+    "url": "https://github.com/ITotalJustice/untitled"
 }