Adjust markdownlint configuration to enforce 4-space indentation for …

…proper mkdocs rendering (#345)

At the moment, unordered list items are not rendered properly on our
index page.
This is because the pre-commit hook `markdownlint` was adjusting the
indentation from 4 spaces to 2 spaces for unordered list items. However,
apparently `mkdocs` is failing to understand indentations with 2 spaces
and is rendering nested items at the same level as parent items.

With this PR, I am setting the indentation to 4 for the markdownlint
hook to allow proper rendering of unordered list items with mkdocs.

You can check the before and after images to verify the indentation
getting fixed with this PR.
## Before
<img width="647" alt="Screenshot 2025-01-07 at 4 04 17 PM"
src="https://github.com/user-attachments/assets/48fc20a8-7641-4120-81af-3abb0d8f3393"
/>


## After
<img width="673" alt="Screenshot 2025-01-07 at 4 04 56 PM"
src="https://github.com/user-attachments/assets/76c8066f-5710-4828-83c8-330cacae2055"
/>

.markdownlint.json

@@ -0,0 +1,5 @@
+{
+  "MD007": {
+    "indent": 4
+  }
+}

docs/index.md

@@ -7,23 +7,23 @@ Everything you need to know about how to build Apache Airflow® workflows using
 Are you new to DAG Factory? This is the place to start!
 
 * DAG Factory at a glance
-  * [Quickstart with Airflow standalone](getting-started/quick-start-airflow-standalone.md)
-  * [Quickstart with Astro CLI](getting-started/quick-start-astro-cli.md)
+    * [Quickstart with Airflow standalone](getting-started/quick-start-airflow-standalone.md)
+    * [Quickstart with Astro CLI](getting-started/quick-start-astro-cli.md)
 * Install guide
 * [Using YAML instead of Python](./comparison/index.md)
-  * [Traditional Airflow Operators](./comparison/traditional_operators.md)
-  * [TaskFlow API](./comparison/taskflow_api.md)
+    * [Traditional Airflow Operators](./comparison/traditional_operators.md)
+    * [TaskFlow API](./comparison/taskflow_api.md)
 
 ## Configuration
 
 * [Configuring your workflows](configuration/configuring_workflows.md)
-  * [Environment variables](configuration/environment_variables.md)
-  * [Defaults](configuration/defaults.md)
+    * [Environment variables](configuration/environment_variables.md)
+    * [Defaults](configuration/defaults.md)
 
 ## Features
 
 * Dynamically creating tasks during runtime
-  * Dynamic task mapping
+    * Dynamic task mapping
 
 ## Getting help