docs: Add documentation supporting native, asynchronous database operations (#580)

* feat: add sea orm documents

* feat: add description for sea orm cli

examples/sea-orm-databases/src/users.rs

@@ -0,0 +1,16 @@
+//! `SeaORM` Entity, @generated by sea-orm-codegen 1.1.4
+
+use sea_orm::entity::prelude::*;
+
+#[derive(Clone, Debug, PartialEq, DeriveEntityModel, Eq)]
+#[sea_orm(table_name = "users")]
+pub struct Model {
+    #[sea_orm(primary_key, auto_increment = false)]
+    pub id: String,
+    pub name: String,
+}
+
+#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
+pub enum Relation {}
+
+impl ActiveModelBehavior for ActiveModel {}