docs: indentation added to "Intallation and usage"

docs/getting_started/installation_and_usage.md

@@ -420,15 +420,15 @@ After that, you can either:
 
 - easily [start a live server to preview the documentation as you write](https://squidfunk.github.io/mkdocs-material/creating-your-site/#previewing-as-you-write)
 
-```shell
-mkdocs serve
-```
+    ```shell
+    mkdocs serve
+    ```
 
 - [build the documentation](https://squidfunk.github.io/mkdocs-material/creating-your-site/#building-your-site)
 
-```shell
-mkdocs build
-```
+    ```shell
+    mkdocs build
+    ```
 
 
 ## Packaging