[CI] Report an error when URLs are missing from an integrations registry entry

[chalin]

• Reformats shortcode to make it easier to read
• Adds to checks for missing URLs, and reports an error (fails the build), when they are missing. (This should probably be a warning, but it matches the other checks that are done.

Note: I know that another partial does similar checks, but maybe not for Integration entries? Anyhow, these checks are now closer to their point of use.

/cc @svrnm

The generated site files are the same (other than the site-build timestamp).

$ (cd public && git diff)                                                                          
diff --git a/site/index.html b/site/index.html
index 4555d76f20..6ed7ea752e 100644
--- a/site/index.html
+++ b/site/index.html
@@ -226,7 +226,7 @@ Attribute Value Netlify built false Deploy context local ">
 <script>
 document.addEventListener("DOMContentLoaded", function() {
   var options = { hour: '2-digit', hour12: false, minute: '2-digit', timeZoneName: 'short' };
-  var buildDate = new Date("2024-08-26T18:49:33-04:00");
+  var buildDate = new Date("2024-08-26T19:26:49-04:00");
   document.getElementById("local-time").innerText = buildDate.toLocaleString(undefined, options);
 });
 </script>

[theletterf]

Nice!