Add info for cookies that set by Analytics.js

Author: joeynmq

src/connections/sources/catalog/libraries/website/javascript/index.md

@@ -783,6 +783,25 @@ The snippet asynchronously requests and loads a customized JavaScript bundle (`a
 
 Without any destinations enabled, the `analytics.min.js` file is about 62KB. Each time you enable a destination, the file's size may increase slightly.
 
+### Cookies set by Analytics.js
+
+Segment sets three cookies in general:
+| Cookie             | Description                                                                       |
+| ------------------ | --------------------------------------------------------------------------------- |
+| `ajs_anonymous_id` | An anonymous ID generated by Analytics.js, used for Segment calls.                |
+| `ajs_group_id`     | A group ID that can be specified by making a `group()` call with Analytics.js.    |
+| `ajs_user_id`      | A user ID that can be specified by making an `identify()` call with Analytics.js. |
+ 
+These cookies expire by default **one** year after the date created. 
+ 
+Some user/group traits are also stored in `localStorage`:
+| Cookie                 | Description                                         |
+| ---------------------- | --------------------------------------------------- |
+| `ajs_user_traits`      | The traits that are passed in an `identify()` call. |
+| `ajs_group_properties` | The properties that are passed in a `group()` call. |
+ 
+The `localStorage` variables don't have an expiry, as that functionality is defined by the browser.
+
 ### Local storage cookies used by Analytics.js
 
 Analytics.js uses `localstorage` cookies if you have retries enabled, to keep track of retry timing.