Update media.mdx explaining that getScreenshotUrl currently doesn't work in DX12 games.

website/pages/docs/api/media/media.mdx

@@ -199,6 +199,17 @@ overwolf.media.getScreenshotUrl(
 );
 ```
 
+### Known Issues
+overwolf.media.getScreenshotUrl in any DX12 game always returns the following result:
+```json
+{
+  success: false,
+  status: 'error',
+  error: 'Capture failed'
+}
+```
+This is a known limitation of the current implementation.  There is a workaround using overwolf.media.takeScreenshot and deleting the screenshot afterward but it's less performant.
+
 ## shareImage(image, description, callback)
 #### Version added: 0.78
 
@@ -503,4 +514,4 @@ url             |  string
   "success": true,
   "url": ""
 }
-```
+```