Add missing module dependencies

Add dependencies on modules 'mediawiki.api' and 'mediawiki.user'.

This change prevents the error
> Uncaught TypeError: mw.user.isNamed is not a function
when loading this extension with debug mode.

Change-Id: I12cb544dc91cc339781b6a31a4a699a4fa023a9b

extension.json

@@ -40,6 +40,8 @@
 		"ext.DarkMode": {
 			"es6": true,
 			"dependencies": [
+				"mediawiki.api",
+				"mediawiki.user",
 				"oojs-ui.styles.icons-accessibility"
 			],
 			"packageFiles": [