fix(contented-pipeline-md): replace \n in description to fix SEO (#579

)

#### What this PR does / why we need it:

As per title.

packages/contented-pipeline-md/src/plugins/RemarkFrontmatter.ts

@@ -40,7 +40,7 @@ function visitDescription(file: VFile): (node: Paragraph) => void {
       return;
     }
 
-    contented.fields.description = toString(node).substring(0, 300);
+    contented.fields.description = toString(node).replaceAll('\n', ' ').substring(0, 300);
   };
 }