Move source files to src dir

CMakeLists.txt

@@ -16,10 +16,10 @@ find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Widgets)
 find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Widgets)
 
 set(PROJECT_SOURCES
-    main.cpp
+    src/main.cpp
-    mainwindow.cpp
+    src/mainwindow.cpp
-    mainwindow.h
+    src/mainwindow.h
-    mainwindow.ui
+    src/mainwindow.ui
 )
 
 if(${QT_VERSION_MAJOR} GREATER_EQUAL 6)