* install: unify the style of installation steps.

module/install/ui/progress.html.php

@@ -74,10 +74,12 @@ if(!helper::isAjaxRequest('modal'))
 
 div
 (
-    set::id('main'),
+    setID('main'),
+    setClass('flex justify-center'),
     div
     (
-        set::id('mainContent'),
+        setID('mainContent'),
+        setClass('px-1 mt-2 w-full max-w-7xl'),
         h::importCss($app->getWebRoot() . 'js/xterm/xterm.css'),
         set('data-loading', $lang->solution->notices->uninstallingSolution),
         formPanel