dev: add db:migrate:undo script

Author: dyc3

package.json

@@ -27,7 +27,8 @@
     "api-server": "yarn workspace ott-server debug",
     "dev": "NODE_ENV=development concurrently \"yarn run api-server\" \"PORT=8080 yarn run serve\"",
     "dev-windows": "SET NODE_ENV=development&&concurrently \"npm:api-server\" \"npm:serve\"",
-    "db:migrate": "yarn workspace ott-server run sequelize db:migrate"
+    "db:migrate": "yarn workspace ott-server run sequelize db:migrate",
+    "db:migrate:undo": "yarn workspace ott-server run sequelize db:migrate:undo"
   },
   "dependencies": {
     "ansi-colors": "^4.1.1",