Add brand new Dagster project example to dbt quickstart (#21816)

## Summary & Motivation

This PR updates the quickstart example for dbt + Dagster - it adds the
steps to create a brand new Dagster project using the scaffold to wrap a
dbt project.

This work is the continuation of #21240 

## How I Tested These Changes

BK 
+
local
```
make mdx-full-format
make next-watch-build
```

docs/content/integrations/dbt/quickstart.mdx

@@ -41,6 +41,33 @@ The `dagster-dbt` library installs both `dbt-core` and `dagster` as dependencies
 
 ---
 
+## Load your dbt project in Dagster
+
+<TabGroup>
+<TabItem name="Option 1: Create a new Dagster project">
+
+### Option 1: Create a new Dagster project
+
+You can create a Dagster project that wraps your dbt project by using the `dagster-dbt` command line interface.
+
+To use the command, you'll need to provide two options:
+
+- `--project-name`, the name of your Dagster project to be created, and
+- `--dbt-project-dir`, the path to your dbt project.
+
+In our example, our Dagster project is named `my_dagster_project` and the relative path to our dbt project is `./my_dbt_project`, meaning that we are in the directory where `my_dbt_project` is located.
+
+```shell
+dagster-dbt project scaffold --project-name my_dagster_project --dbt-project-dir ./my_dbt_project --use-experimental-dbt-project
+```
+
+This command creates a new directory called `my_dagster_project/` inside the current directory. The new `my_dagster_project/` directory will contain a set of files that define a Dagster project to load the dbt project provided in `./my_dbt_project`.
+
+</TabItem>
+</TabGroup>
+
+---
+
 ## Run your dbt project in Dagster's UI
 
 Now that your code is ready, you can run Dagster's UI to take a look at your dbt project.