MINOR: Supress whitespace cleanup in thirdparty folders.

The whitespace cleanup specified by editorconfig shouldn't happen on thirdparty
files, as these should be left alone.

.editorconfig

@@ -16,3 +16,13 @@ trim_trailing_whitespace = false
 [*.yml]
 indent_size = 2
 indent_style = space
+
+# Don't perform any clean-up on thirdparty files
+
+[thirdparty/**]
+trim_trailing_whitespace = false
+insert_final_newline = false
+
+[admin/thirdparty/**]
+trim_trailing_whitespace = false
+insert_final_newline = false