fix: accept application/ld+json when fetching context (#19)

Co-authored-by: Haninn <[email protected]>

src/3.0/validate/validate.ts

@@ -56,7 +56,7 @@ const documentLoader = async (url: string) => {
     for (const url of preloadedContextList) {
       contexts.set(
         url,
-        fetch(url, { headers: { accept: "application/json" } }).then((res: any) => res.json()),
+        fetch(url, { headers: { accept: "application/json, application/ld+json" } }).then((res: any) => res.json()),
       );
     }
   }