Update README.md

Corrected some stupid mistakes.
Projekt QtCreatora
MainWindow UI
IdRegisteredClass
IdRegisteredClass
ItemEventHandlers
Zmienione nazwy typedefow dla IdRegisteredClass
SystemViewItem + SystemScene
SystemView namespace & SystemScene::stateMachine
brakujacy include
IdType typedefs
MainWindow setup1
fixed (yet) non-existing states & items handling
AddStaffState
SystemScene handlers
SystemScene handlers hidden
HANDLER macro
SystemImageItem
SystemImageItem constructor fixed
Image loading