Add fixme comment

Author: CrSjimo

src/appcore/doc/filelocker.cpp

@@ -329,6 +329,7 @@ namespace Core {
         d->filePath = path;
 
         // Add new file to watcher
+        // FIXME macOS watcher erroneously detects the change made by this program itself
         d->watcher->addPath(path);
 
         // Reset modification flag after successful saveAs