This feature has been already available for iOS devices.

This now also available in Outlook Mobile for Android devices.

When you click the Search button in Outlook Mobile you will now have access to your files (including attachments).

When you click on the Files section you have access to a complete and detailed list of all files

The file feed functionality requires you (or your administrator) has enabled Microsoft Graph (see https://docs.microsoft.com/en-gb/sharepoint/delve-for-office-365-admins#control-access-to-the-office-graph)