feat: hook color picker to entry fields

src/ui/uicontroller.h

@@ -12,6 +12,7 @@ all the widgets used in internal logic of the program
 typedef struct VektorWidgetState {
     GtkWindow* window;
     GtkPaned* workspacePaned;
+    GtkPaned* sidepanelPaned;
     GtkGLArea* workspaceCanvas;
 
     GtkButton* workspaceButtonMasterShapes;
@@ -22,6 +23,10 @@ typedef struct VektorWidgetState {
 
     VektorColorWheel* workspaceColorPicker;
 
+    GtkEntry* sidepanelEntryR;
+    GtkEntry* sidepanelEntryG;
+    GtkEntry* sidepanelEntryB;
+
     // GtkWidget* Workspace
 } VektorWidgetState;