Update YAML schema documentation page

docs/yaml_schema.md

@@ -5,12 +5,19 @@ hide:
 
 # YAML Schema
 
+The YAML schema is the key abstraction which allows similar workflows for
+performance analysis to be captured by this single tool.
+
+Pydantic is used to parse the YAML file, and as such a full description of the
+YAML schema can be seen in the entity-relationship diagram of the Pydantic
+model, shown below.
+
 <figure markdown="span">
-  ![Viewing run configurations](./assets/images/uml/yaml_model){ loading=lazy }
+  ![Viewing run configurations](./assets/images/uml/yaml_model.png){ loading=lazy }
   <figcaption>A diagram of the Pydantic model used to parse the YAML schema, generated using erdantic.</figcaption>
 </figure>
 
-## Run Configurations
+<!-- ## Run Configurations
 
 ## Test Benches
 
@@ -22,4 +29,4 @@ hide:
 
 #### Metrics
 
-#### Plotting
+#### Plotting -->