create-app: Add changeset for techdocs-backend changes around GCS publisher

.changeset/six-mugs-camp.md

@@ -0,0 +1,20 @@
+---
+'@backstage/create-app': patch
+---
+
+In the techdocs-backend plugin (`packages/backend/src/plugins/techdocs.ts`), create a publisher using
+
+```
+  const publisher = Publisher.fromConfig(config, logger, discovery);
+```
+
+instead of
+
+```
+  const publisher = new LocalPublish(logger, discovery);
+```
+
+An instance of `publisher` can either be a local filesystem publisher or a Google Cloud Storage publisher.
+
+Read more about the configs here https://backstage.io/docs/features/techdocs/configuration
+(You will also have to update `techdocs.storage.type` to `local` or `google_gcs`. And `techdocs.builder` to either `local` or `ci`.)