doc/tutorial: add skeleton and initial posts (#1317)

doc/md/tutorial-setup.md

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+---
+id: tutorial-setup
+title: Setting Up
+sidebar_label: Setting Up
+---
+
+This guide is intended for first-time users who want instructions on how to set up an Ent project from scratch.
+Before we get started, make sure you have the following prerequisites installed on your machine.
+
+## Prerequisites
+
+- [Go](https://golang.org/doc/install)
+- [Docker](https://docs.docker.com/get-docker) (optional)
+
+After installing these dependencies, create a directory for the project and initialize a Go module:
+
+```console
+mkdir todo
+cd $_
+go mod init todo
+```
+
+## Installation
+
+Run the following Go commands to install Ent, and tell it to initialize the project structure along with a `Todo` schema.
+
+```console
+go get entgo.io/ent/cmd/ent
+```
+
+```console
+go run entgo.io/ent/cmd/ent init Todo
+```
+
+After installing Ent and running `ent init`, your project directory should look like this:
+
+```console
+.
+├── ent
+│   ├── generate.go
+│   └── schema
+│       └── todo.go
+├── go.mod
+└── go.sum
+```
+
+The `ent` directory holds the generated assets (see the next section), and the `ent/schema` directory contains your
+entity schemas.
+
+## Code Generation
+
+When we ran `ent init Todo` above, a schema named `Todo`  was created in the `todo.go` file under the`todo/ent/schema/` directory:
+
+```go
+package schema
+
+import "entgo.io/ent"
+
+// Todo holds the schema definition for the Todo entity.
+type Todo struct {
+	ent.Schema
+}
+
+// Fields of the Todo.
+func (Todo) Fields() []ent.Field {
+	return nil
+}
+
+// Edges of the Todo.
+func (Todo) Edges() []ent.Edge {
+	return nil
+}
+```
+
+As you can see, initially, the schema has no fields or edges defined. Let's run the command for generating assets to interact with
+the `Todo` entity:
+
+```console
+go generate ./ent
+```
+
+## Create a Test Case
+
+Running `go generate ./ent` invoked Ent's automatic code generation tool, which uses the schemas we define in our `schema` package to generate the actual Go code which we will now use to interact with a database. At this stage, you can find under `./ent/client.go`, client code that is capable of  querying and mutating the `Todo` entities. Let's create a
+[testable example](https://blog.golang.org/examples) to use this. We'll use [SQLite](https://github.com/mattn/go-sqlite3)
+in this test-case for testing Ent.
+
+```console
+go get github.com/mattn/go-sqlite3
+touch example_test.go
+```
+
+Paste the following code in `example_test.go` that instantiates an `ent.Client` and automatically creates all schema resources
+in the database (tables, columns, etc).
+
+```go
+package main
+
+import (
+	"context"
+	"log"
+	"todo/ent"
+
+	"entgo.io/ent/dialect"
+	_ "github.com/mattn/go-sqlite3"
+)
+
+func Example_Todo() {
+	// Create an ent.Client with in-memory SQLite database.
+	client, err := ent.Open(dialect.SQLite, "file:ent?mode=memory&cache=shared&_fk=1")
+	if err != nil {
+		log.Fatalf("failed opening connection to sqlite: %v", err)
+	}
+	defer client.Close()
+	ctx := context.Background()
+	// Run the automatic migration tool to create all schema resources.
+	if err := client.Schema.Create(ctx); err != nil {
+		log.Fatalf("failed creating schema resources: %v", err)
+	}
+	// Output:
+}
+```
+
+Then, run `go test` to verify that everything works as expected.
+
+```console
+go test
+```
+
+After setting up our project, we're ready to create our Todo list.