feat: add persistence

Author: amertak

gdi/get-data-in/rum/browser/configure-rum-browser-instrumentation.rst

@@ -85,6 +85,9 @@ Use the following settings to configure the Browser RUM agent:
    * - ``debug``
      - Boolean
      - Activates debug logging in the developer console. The default value is ``false``.
+   * - ``persistence``
+     - ``cookie`` | ``localStorage``
+     - Specifies where session data should be stored. The default value is ``cookie``. Available from version ``0.20.0``.
    * - ``disableBots``
      - Boolean
      - Disables tracking of bots. The default value is ``false``. Available from version ``0.20.0``.