fill services.yaml for downloader (#27553)

homeassistant/components/downloader/services.yaml

@@ -0,0 +1,15 @@
+download_file:
+  description: Downloads a file to the download location.
+  fields:
+    url: 
+      description: The URL of the file to download.
+      example: 'http://example.org/myfile'
+    subdir:
+      description: Download into subdirectory.
+      example: 'download_dir'
+    filename:
+      description: Determine the filename.
+      example: 'my_file_name'
+    overwrite:
+      description: Whether to overwrite the file or not.
+      example: 'false'