新增：项目数据集模型

db/migrate/20240401030707_create_project_datasets.rb

@@ -0,0 +1,11 @@
+class CreateProjectDatasets < ActiveRecord::Migration[5.2]
+  def change
+    create_table :project_datasets do |t|
+      t.string :title 
+      t.text :description
+      t.references :project
+
+      t.timestamps
+    end
+  end
+end