Add page referrer on Gelbooru

package.json

@@ -1,6 +1,6 @@
 {
   "name": "neo-scraper",
-  "version": "0.11.0",
+  "version": "0.11.1",
   "description": "Scrape a booru-like post object from the DOM.",
   "type": "module",
   "main": "dist/index.js",

src/engines/Gelbooru.ts

@@ -179,6 +179,7 @@ export default class Gelbooru extends ScrapeEngineBase {
     }
     // End of code duplication with Danbooru engine.
 
+    post.referrer = document.location.origin;
     result.tryAddPost(post);
 
     return result;