Add patch rollback page (#282)

* Add patch rollback page

* add image alt text

* spellcheck

* explain the "out of patches" case

src/content/docs/code-push/rollback.mdx

@@ -0,0 +1,49 @@
+---
+title: Roll back a Patch
+description: Learn how to roll back a patch in Shorebird.
+sidebar:
+  label: Rollback
+  order: 5
+---
+
+If you discover that a live patch has a bug, Shorebird supports patch roll back.
+When a patch is rolled back, it is remotely uninstalled from end users' devices
+and replaced by either the previous patch or the base release if no previous
+patch is available.
+
+## How to roll back a patch
+
+In the [Shorebird Console](https://console.shorebird.dev/), navigate to the
+release that contains the patch you want to roll back. On the right side of the
+patch row, click the "more" icon (three vertical dots) and select "Rollback":
+
+![The Shorebird Console showing a "roll back patch" button](https://github.com/user-attachments/assets/941fdc46-d0f3-463f-835f-5c8eb8a02e83)
+
+## What happens when a patch is rolled back?
+
+Imagine we have a release with three patches:
+
+![The Shorebird Console showing three patches, with patch 3 as the active patch](https://github.com/user-attachments/assets/ee5d4e2b-eca3-4318-99e9-038c0134bfff)
+
+When a user downloads this release from the store, Shorebird will see that patch
+3 is the latest available patch and download it.
+
+If we discover that there is a problem with patch 3, we can roll it back. The
+Console will look like this after a rollback:
+
+![The Shorebird Console showing three patches, with patch 3 rolled back and patch 2 as the active patch](https://github.com/user-attachments/assets/7ba4ff2c-5823-4c9f-a260-68ca6ce1e10a)
+
+Users who download the app from the store will now get patch 2 instead of patch 3. Users who already had patch 3 installed will be downgraded to patch 2.
+
+### Under the hood
+
+When a Shorebird app checks for new patches, the server includes in its response
+a list of rolled back patches. If the device has any rolled back patches
+installed, it deletes them and reverts to the last "good" patch, which will be
+visible the next time the app starts.
+
+:::note
+If you app needs to download an older patch as part of a rollback,
+installing that patch will count against your monthly patch installs. If you
+have no remaining patch installs, the app will revert to the base release.
+:::