fix: content url for private repo

Author: matzkoh

src/plugin.js

@@ -39,6 +39,7 @@ function getContentURL(config, filePath) {
     if (config.private) {
         return urlJoin(
             location.origin,
+            config.repo.split('/')[1],
             "gitbook/gitbook-plugin-github-issue-feedback/contents",
             filePath
         );
@@ -95,4 +96,4 @@ window.require(["gitbook"], function(gitbook) {
         document.body.appendChild(reportElement);
     });
 
-});
+});