Add existing Dagster project example to dbt quickstart

[maximearmstrong]

Summary & Motivation

This PR updates the quickstart example for dbt + Dagster - it adds the steps to update an existing Dagster project to wrap a dbt project.

This work is the continuation of #21240 and #21816

How I Tested These Changes

BK
+
local

make mdx-full-format
make next-watch-build

[maximearmstrong]

• Add existing Dagster project example to dbt quickstart #21817 👈
• Add quickstart example for dbt & Dagster #21240 : 2 other dependent PRs (#21568 , #21816 )
• Add dbt + Dagster+ guide #21229 : 1 other dependent PR (#21950 )
• master

This stack of pull requests is managed by Graphite. Learn more about stacking.

Join @maximearmstrong and the rest of your teammates on Graphite

[rexledesma]

We should show the file structure that we expect as a directory tree to be explicit about where we expect files to be.

[maximearmstrong]

Done in ce9d1a1

[rexledesma]

We should have placeholders for their existing assets, jobs, resources, etc.

[maximearmstrong]

Done in ce9d1a1

[rexledesma]

Suggested change

	<TabItem name="Option 2: Use an existing Dagster project">
	<TabItem name="Option 2: Load your dbt project in an existing Dagster project">

[maximearmstrong]

Done in ce9d1a1

[rexledesma]

See comment on how to format the placeholder

[rexledesma]

Use ...

Suggested change

	defs = Definitions(
	assets=[
	# your other assets here,
	my_dbt_assets
	],
	jobs=[
	# your jobs here
	],
	resources={
	# your other resources here,
	"dbt": DbtCliResource(project_dir=my_project),
	},
	)
	# end_dbt_definitions_example
	defs = Definitions(
	...,
	assets=[
	...,
	# Add the dbt assets alongside your other assets
	my_dbt_assets
	],
	resources={
	...
	# Add the dbt resource alongside your other resources
	"dbt": DbtCliResource(project_dir=my_project),
	},
	)
	# end_dbt_definitions_example