docs: Provide iframe embed solution (#440)

* Provide iframe embed solution

* Update index.mdx

Author: tonysurfly

docs/widgets/iframe/index.mdx

@@ -42,8 +42,24 @@ for security reasons, as users could easily be tricked
 by embeding the original site on a malicious page.
 
 Some proxies disallow iframes by default for this reason.
-You can use https://iframetester.com/ to check, if the site is allowing iframes.
-If you manage all of your own applications, you can usually change that.
+You can use https://iframetest.com to check, if the site is allowing iframes.
+
+If you manage all of your own applications, you can usually change that by configuring
+the appropriate headers (such as `X-Frame-Options` or `Content-Security-Policy`) to allow iframes.
+
+For example, to allow your site to be embedded in iframes from specific domains:
+
+**Apache (.htaccess or httpd.conf):**
+```apache
+Header set Content-Security-Policy "frame-ancestors 'self' https://trusted-domain.com"
+Header set X-Frame-Options "ALLOW-FROM https://trusted-domain.com"
+```
+
+**Nginx:**
+```nginx
+add_header Content-Security-Policy "frame-ancestors 'self' https://trusted-domain.com";
+add_header X-Frame-Options "ALLOW-FROM https://trusted-domain.com";
+```
 
 ### Example URLs