docs: add a section about upgrading plan to Teams

src/content/docs/teams.mdx

@@ -8,6 +8,24 @@ collaborators to an app. Shorebird free "Hobby" users can upgrade
 to the Teams tier to add collaborators via a link in the
 [Shorebird console](https://console.shorebird.dev).
 
+## Upgrading to Teams
+
+You can manage your account and billing at any time via
+https://console.shorebird.dev/account
+
+There is an "Edit" drop-down there, and from within that an "Upgrade Account"
+option which will present you a pop-up dialog and allow you to chose the plan
+you wish to upgrade to.
+
+There is a slider control at the bottom of the dialog which allows choosing
+different plan levels.
+
+If you do not see the plan you're expecting, please reach out to
+[email protected] we'd be happy to work with you.
+
+Once you've upgraded to a Teams plan, you have the ability to manage
+Collaborators on a per-app level.
+
 ## Managing Collaborators
 
 Collaborators can be managed on the Shorebird console. To add a collaborator,