serve pages for errors not in debug

{{cookiecutter.repo_name}}/{{cookiecutter.repo_name}}/static_source/js/main.ts

@@ -33,6 +33,19 @@ htmx.defineExtension("get-timezone", {
   }
 });
 
+// This function will listen for HTMX errors and display the appropriate page
+// as needed. Without debug mode enabled, HTMX will normally refuse to
+// serve any HTML attached to an HTTP error code. This will allow us to present
+// users with custom error pages.
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+htmx.on("htmx:beforeOnLoad", (event:any) => {
+  const { xhr } = event.detail;
+  if (xhr.status === 500 || xhr.status === 404) {
+    event.stopPropagation();
+    document.children[0].innerHTML = xhr.response;
+  }
+});
+
 if (import.meta.hot) {
   import.meta.hot.on("template-hmr", () => {
     const dest = document.location.href;