• Removed deprecated argument handling from Mojo::Promise::new.
  
• Removed experimental status from all_settled method in Mojo::Promise.
  
• Removed experimental status from content_type and file_type methods in Mojolicious::Types.
  
• Removed experimental status from cleanup event in Mojo::IOLoop::Subprocess.
  
• Switched from Storable to JSON serialization for Mojo::IOLoop::Subprocess IPC to increase efficiency.
  
• Added exit_code method to Mojo::IOLoop::Subprocess.
  
• Improved Mojo::Promise to warn when an unhandled rejected promise is destroyed.
  
• Fixed a bug where the resolve class method in Mojo::Promise would unnecessarily create new promises.
  
• Fixed a promise chaining bug in Mojo::Promise. (karjala)