docs: add closeModal() API documentation for embed instructions

- Add comprehensive closeModal() documentation to embed-instructions.mdx
- Include usage examples for both namespaced and non-namespaced embeds
- Add common use case example in embed-events.mdx
- Document supported embed types and error handling
- Include migration note from internal API

Co-Authored-By: hariom@cal.com <hariombalhara@gmail.com>

Author: devin-ai-integration[bot]

embedding/embed-instructions.mdx

@@ -39,4 +39,25 @@ To open cal link on some action, make it pop open instantly by using `preload`.
 </script>
 ```
 
-- `calLink` - Cal Link that you want to embed e.g. john. Just give the username. No need to give the full URL https://cal.com/john
+- `calLink` - Cal Link that you want to embed e.g. john. Just give the username. No need to give the full URL https://cal.com/john
+
+#### Close modal
+
+Programmatically closes a modal-based embed shown as a pop-up (for example, when opened via an element click or the floating button).
+
+```js
+<script>
+  Cal("closeModal");
+</script>
+```
+
+**Supported embed types:**
+- Pop-up via element click
+- Floating button pop-up
+
+**Namespaced usage:**
+```js
+<script>
+  Cal.ns.yournamespace("closeModal");
+</script>
+```