fix: [DebugBar] Toolbar display may be broken

[kenjis]

Description
From https://forum.codeigniter.com/showthread.php?tid=90624

If a dev changes CSS for h1, the toolbar dislpay will be broken.

Before:

After:

--- a/app/Views/welcome_message.php
+++ b/app/Views/welcome_message.php
@@ -34,6 +34,16 @@
         .menu {
             padding: .4rem 2rem;
         }
+        h1 {
+            font-size: 1.8em;
+            font-weight: 400;
+            font-family:'Open Sans', Sans-serif;
+            text-transform: uppercase;
+            color: #464646;
+            background-color: #f4f9eb;
+            padding: 1.4em 0 1.4em 20px;
+            margin: 0 0 1em;
+        }
         header ul {
             border-bottom: 1px solid rgba(242, 242, 242, 1);
             list-style-type: none;

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide