Add todo example, remove yarn, change schema structure, update readme

apps/cli/template/with-prisma-postgres/packages/server/prisma/schema/auth.prisma

@@ -1,20 +1,3 @@
-generator client {
-  provider = "prisma-client-js"
-}
-
-datasource db {
-  provider = "postgres"
-  url      = env("DATABASE_URL")
-}
-
-model Todo {
-  id        Int     @id @default(autoincrement())
-  text      String
-  completed Boolean @default(false)
-
-  @@map("todo")
-}
-
 model User {
   id            String    @id @map("_id")
   name          String

apps/cli/template/with-prisma-postgres/packages/server/prisma/schema/schema.prisma

@@ -0,0 +1,9 @@
+generator client {
+  provider = "prisma-client-js"
+  previewFeatures = ["prismaSchemaFolder"]
+}
+
+datasource db {
+  provider = "postgres"
+  url      = env("DATABASE_URL")
+}

apps/cli/template/with-prisma-postgres/packages/server/prisma/schema/todo.prisma

@@ -1,12 +1,3 @@
-generator client {
-  provider = "prisma-client-js"
-}
-
-datasource db {
-  provider = "postgres"
-  url      = env("DATABASE_URL")
-}
-
 model Todo {
   id        Int     @id @default(autoincrement())
   text      String