Fix sitemap URLs (#3220)

Author: gregberge

.changeset/healthy-parrots-call.md

@@ -0,0 +1,6 @@
+---
+"gitbook-v2": patch
+"gitbook": patch
+---
+
+Fix URL in sitemap

packages/gitbook-v2/src/lib/links.ts

@@ -93,6 +93,11 @@ export function createLinker(
         },
 
         toAbsoluteURL(absolutePath: string): string {
+            // If the path is already a full URL, we return it as is.
+            if (URL.canParse(absolutePath)) {
+                return absolutePath;
+            }
+
             if (!servedOn.host) {
                 return absolutePath;
             }