feat: multitab and basic file saving

CMakeLists.txt

@@ -33,6 +33,8 @@ PRIVATE
     main.cpp
     mainwindow.cpp mainwindow.h
     sciedit.cpp sciedit.h
+    tabwidget.cpp tabwidget.h
+    documentmanager.cpp documentmanager.h
     editorviewhelper.cpp editorviewhelper.h
     generalsettings.ui