add docs on seeding local database (#775)

docs/src/getting-started/local-development.md

@@ -1 +1,19 @@
 # Local Development
+
+## Seeding Local Database
+
+A seeded database is required for some pages on the frontend.
+
+```sh
+# ./berkeleytime
+
+# Ensure the MongoDB instance is already running.
+docker compose up -d
+
+# Download the data
+curl -O https://storage.googleapis.com/berkeleytime/public/stage_backup.gz
+
+# Copy the data and restore
+docker cp ./stage_backup.gz berkeleytime-mongodb-1:/tmp/stage_backup.gz
+docker exec berkeleytime-mongodb-1 mongorestore --drop --gzip --archive=/tmp/stage_backup.gz
+```