feat: add logic for the modrinth instance modpack page

Signed-off-by: flow <flowlnlnln@gmail.com>

launcher/modplatform/modrinth/ModrinthPackManifest.h

@@ -80,6 +80,7 @@ struct ModpackExtra {
 struct ModpackVersion {
     QString name;
     QString version;
+    QString changelog;
 
     QString id;
     QString project_id;