docs(json-schema): set markdownDescription for rich-text editor previews (#41894)

Editors such as VSCode will look for `markdownDescription` to render the
description, if present, and will render that as Markdown, instead of
plain text.

Author: jamietanna

tools/docs/schema.ts

@@ -55,6 +55,7 @@ function createSingleConfig(option: RenovateOptions): Record<string, unknown> {
   } & Omit<Partial<RenovateOptions>, 'type'> = {};
   if (option.description) {
     temp.description = option.description;
+    temp.markdownDescription = option.description;
   }
   temp.type = option.type;
   if (option.type === 'array') {