[BUG] Center icon and callout text

- Wrap the icon and callout into a seperate `<p>` which has `display:
flex; align-items: center` set. To center the icon with the callout text.
- Resolves #3006

(cherry picked from commit 6ffae461d4)

web_src/css/base.css

@@ -1127,6 +1127,11 @@ input:-webkit-autofill:active,
   margin: auto 0.5em auto 0;
 }
 
+.attention-title {
+  align-items: center;
+  display: flex;
+}
+
 blockquote.attention-note {
   border-left-color: var(--color-blue-dark-1);
 }