Undostack: Introduce undostack

Right now we're using QUndoStack which is from Qt library, although it
has limited usage which we want to expand since we want to handle errors
in a proper way without any hacks regarding QUndoStack, so these series
of patches will introduce customly made Undostack, as well as Command
class which will replace QUndoCommand/QUndoStack classes.

CMakeLists.txt

@@ -43,6 +43,10 @@ set(PROJECT_SOURCES
         source/openasdialog.cpp
         source/palettewidget.cpp
         source/settingsdialog.cpp
+        source/undostack.cpp
+        source/undostack.h
+        source/command.cpp
+        source/command.h
 )
 
 if(${QT_VERSION_MAJOR} GREATER_EQUAL 6)

source/command.cpp

@@ -0,0 +1,2 @@
+#include "command.h"
+

source/command.h

@@ -0,0 +1,6 @@
+#pragma once
+
+
+class Command {
+
+};

source/undostack.cpp

@@ -0,0 +1 @@
+#include "undostack.h"

source/undostack.h

@@ -0,0 +1,8 @@
+#pragma once
+
+#include "command.h"
+
+class UndoStack {
+private:
+    std::vector<Command> cmds;
+};