db [nfc]: Mention build_runner for schema changes

Signed-off-by: Zixuan James Li <[email protected]>

Author: PIG208

lib/model/database.dart

@@ -53,8 +53,11 @@ class AppDatabase extends _$AppDatabase {
 
   // When updating the schema:
   //  * Make the change in the table classes, and bump schemaVersion.
-  //  * Export the new schema and generate test migrations:
+  //  * Export the new schema and generate test migrations with drift:
   //    $ tools/check --fix drift
+  //    and generate database code with build_runner.
+  //    See ../../README.md#generated-files for more
+  //    information on using the build_runner.
   //  * Write a migration in `onUpgrade` below.
   //  * Write tests.
   @override