Add documentation for /supervisor/available_updates (#1135)

docs/api/supervisor/endpoints.md

@@ -2270,6 +2270,54 @@ Returns information about the security features
 
 ### Supervisor
 
+<ApiEndpoint path="/supervisor/available_updates" method="get">
+
+Returns information about available updates
+
+**Example response:**
+
+```json
+{
+  "available_updates": [
+  {
+      "panel_path": "/update-available/core",
+      "update_type": "core",
+      "version_latest": "321",
+    },
+    {
+      "panel_path": "/update-available/os",
+      "update_type": "os",
+      "version_latest": "321",
+    },
+    {
+      "panel_path": "/update-available/supervisor",
+      "update_type": "supervisor",
+      "version_latest": "321",
+    },
+    {
+      "name": "Awesome addon",
+      "icon": "/addons/awesome_addon/icon",
+      "panel_path": "/update-available/awesome_addon",
+      "update_type": "addon",
+      "version_latest": "321",
+    }
+  ]
+}
+```
+
+**Returned data:**
+
+| key | type | description |
+-- | -- | --
+update_type | string | `addon`, `os`, `core` or `supervisor`
+name | string | Returns the name (only if the `update_type` is `addon`)
+icon | string | Returns the path for the icon if any (only if the `update_type` is `addon`)
+version_latest | string | Returns the available version
+panel_path | string | Returns path where the UI can be loaded
+
+
+</ApiEndpoint>
+
 <ApiEndpoint path="/supervisor/info" method="get">
 
 Returns information about the supervisor