Add note about pageName screen setting.md

We added a new setting a few months ago and while it appears under the "Settings" in our docs, it is not explicitly explained. This adds an example of how the setting works. Here is the PR for the original change: https://github.com/segmentio/integrations/pull/1722 and JIRA for release last December: https://segment.atlassian.net/browse/CC-7103.

Author: kdaswani

src/connections/destinations/catalog/adobe-analytics/index.md

@@ -105,7 +105,7 @@ Segment's server-side integration is not open-source. Let's explore what happens
 
    For `.page()` events, this XML tag is set as the `category` of the page call, which is sent by providing both `category` and `name` (ie. `.page('Some Category', 'Some Name');`)
 
-3. For `.track()` events, Segment sets `<pageName>` as `properties.pageName`, `properties.page`, `context.page.title`, `context.screen.name` or `'None'` (in order of precedence).
+3. For `.track()` events, Segment sets `<pageName>` as `properties.pageName`, `properties.page`, `context.page.title`, or `context.screen.name` (in order of precedence). If none of these fields are available and **Page Name Fallback to Screen** is enabled, Segment will set `properties.screen` to `<pageName>`.  Otherwise, Segment will fallback on `'None'`.
    For `.page()` calls, Segment sets the tag as the `name`. This can be sent by providing the first parameter: `.page('Some Name');`
 
 4. Since Adobe Analytics does not [support sending timestamped hits a `<visitorID>`](https://marketing.adobe.com/resources/help/en_US/sc/implement/timestamps-overview.html), if you have set your Report to **Timestamp Disabled**, Segment sets `<visitorID>` as these values in order of precedence: