adding info mprec cookies

pages/docs/tracking-methods/sdks/javascript/javascript-replay.mdx

@@ -388,6 +388,24 @@
 
 User replays are stored for 30 days after the time of ingestion by default. Customers with the custom volumes of Session Replay can customize this value between 7 and 365 days as an additional paid add-on. 
 
+### Browser Storage
+
+Session Replay stores temporary replay data in the browser using IndexedDB with dynamically generated key names prefixed with `__mprec_` (short for "Mixpanel Recording"). These keys are used for session recording batchers and are constructed dynamically, for example:
+
+```
+__mprec_<instance_name>_<project_token>_<replay_id>
+```
+
+Where:
+- `__mprec_` identifies the data as Session Replay recording data
+- `<instance_name>` is the Mixpanel instance name (from `getConfig('name')`)
+- `<project_token>` is your Mixpanel project token
+- `<replay_id>` is a unique identifier for the recording session
+
+Each key stores temporary data required to construct a user's Session Replay and is deleted from IndexedDB after the data is successfully sent to Mixpanel.
+
+Some consent management platforms (like Cookiebot) require cookie or storage keys to be pre-declared and may not support dynamically generated names without manual configuration. If you use a CMP, you may need to work with their support team to properly classify these keys.
+
 ## FAQ
 
 #### Can I prevent Session Replay from recording sensitive content?