chore: explain usage of slug over permalink

Signed-off-by: Joshua Castle <26531652+Kas-tle@users.noreply.github.com>

packages/docusaurus-og/src/server/docs.plugin.ts

@@ -88,6 +88,7 @@ export class DocsPlugin {
   }
 
   getHtmlPath = (doc: Partial<DocsPageData>) =>
+    // slug is used here instead of permalink because permalink already contains version and locale paths of websiteOutDir
     doc.metadata?.slug &&
     path.join(this.context.outDir, doc.metadata.slug, 'index.html')
 }