Put Last modified message inside footer tag (#2922)

This is needed so that the color of the text is set according to the
theme.

Before

![image](https://github.com/user-attachments/assets/d8a67cd1-8fef-4530-a3f8-75b755c6481b)

After

![image](https://github.com/user-attachments/assets/ae8e1ac7-9d88-4e0c-aabc-31d7c2ffb1a5)

src/Juvix/Compiler/Backend/Html/Translation/FromTyped/Source.hs

@@ -187,13 +187,15 @@ genModuleHtml o = do
 
     formattedTime :: Sem r Html
     formattedTime =
-      return $
-        Html.span . toHtml $
-          "Last modified on "
-            <> formatTime
-              defaultTimeLocale
-              "%Y-%m-%d %-H:%M %Z"
-              (o ^. genModuleHtmlArgsUTC)
+      return
+        . Html.footer
+        . Html.pre
+        . toHtml
+        $ "Last modified on "
+          <> formatTime
+            defaultTimeLocale
+            "%Y-%m-%d %-H:%M %Z"
+            (o ^. genModuleHtmlArgsUTC)
 
     justCode :: Sem r Html
     justCode =