Prettify JSON in ext.uls.webfonts.repository.js

Use a prettifyed JSON with tabs for indenting. In non-debug mode the
whitespaces get removed by the minimizer.

Change-Id: I17f4ebabccdada3c2ad45a7e0119a4f246de0ebb

scripts/compile-font-repo.php

@@ -31,7 +31,7 @@ class CompileFontRepo extends Maintenance {
 
 		$list = $compiler->getRepository();
 
-		$json = FormatJson::encode( $list );
+		$json = FormatJson::encode( $list, "\t" );
 		$js = <<<JAVASCRIPT
 // Do not edit! This file is generated from data/fontrepo by data/fontrepo/scripts/compile.php
 ( function ( $ ) {