chore: document opt_out_persistence_by_default (#8025)

contents/docs/libraries/js/index.mdx

@@ -505,6 +505,7 @@ Some of the most relevant options are:
 | `mask_all_text`<br/><br/>**Type:** Boolean<br/>**Default:** `false`                                                                                                                       | Prevent PostHog autocapture from capturing any text from your elements.                                                        |
 | `mask_all_element_attributes`<br/><br/>**Type:** Boolean<br/>**Default:** `false`                                                                                                         | Prevent PostHog autocapture from capturing any attributes from your elements.                                                  |
 | `opt_out_capturing_by_default`<br/><br/>**Type:** Boolean<br/>**Default:** `false`                                                                                                        | Determines if users should be opted out of PostHog tracking by default, requiring additional logic to opt them into capturing by calling `posthog.opt_in_capturing`. |
+| `opt_out_persistence_by_default`<br/><br/>**Type:** Boolean<br/>**Default:** `false`                                                                                                        | Determines if users should be opted out of browser data storage by this PostHog instance by default, requiring additional logic to opt them into capturing by calling `posthog.opt_in_capturing`. |
 | `persistence`<br/><br/>**Type:** `localStorage` or `sessionStorage` or `cookie` or `memory` or `localStorage+cookie`<br/>**Default:** `cookie`                                                                | Determines how PostHog stores information about the user. See [persistence](#persistence) for details.                         |
 | `property_denylist`<br/><br/>**Type:** Array<br/>**Default:** `[]`                                                                                                                        | A list of properties that should never be sent with `capture` calls.                                                           |
 | `sanitize_properties`<br/><br/>**Type:** Function<br/>**Default:** `null`                                                                                                                 | A function that allows you to sanitize or modify the properties that get sent. Example: `sanitize_properties: function(properties, event) { if(properties['$ip']) { properties['$ip'] = null } return properties }` |