add db setup to CONTRIBUTING.md

CONTRIBUTING.md

@@ -18,7 +18,8 @@ Before diving into coding, setting up your local environment is key. Here's what
 1. In the root directory, locate the `sample.config.toml` file.
 2. Rename it to `config.toml` and fill in the necessary configuration fields specific to the backend.
 3. Run `npm install` to install dependencies.
-4. Use `npm run dev` to start the backend in development mode.
+4. Run `npm run db:push` to set up the local sqlite.
+5. Use `npm run dev` to start the backend in development mode.
 
 ### Frontend