docs: fix insecure Caddy configuration example (#2827)

The original example only protected the root (`/`) path, leaving other routes unsecured.
* docs: add syntax highlighting for nginx config
* docs: fix headings in `configuration/integration` page
* docs: fix redirect in caddy configuraion example

docs/docusaurus.config.js

@@ -123,7 +123,7 @@ const config = {
       prism: {
         theme: prismThemes.github,
         darkTheme: prismThemes.dracula,
-        additionalLanguages: ['hcl', 'powershell'],
+        additionalLanguages: ['hcl', 'nginx', 'powershell'],
       },
     }),
 };