Update gtk 4.0 assets (#59)

- Add titlebar buttons
- Update assets svg file
- Update assets list file

gtk/src/default/gtk-4.0/assets.txt

@@ -36,6 +36,22 @@ switch-selected
 switch-active-selected
 switch-insensitive-selected
 switch-active-insensitive-selected
+titlebutton-close
+titlebutton-close-backdrop
+titlebutton-close-hover
+titlebutton-close-active
+titlebutton-max
+titlebutton-max-backdrop
+titlebutton-max-hover
+titlebutton-max-active
+titlebutton-min
+titlebutton-min-backdrop
+titlebutton-min-hover
+titlebutton-min-active
+titlebutton-resize
+titlebutton-resize-backdrop
+titlebutton-resize-hover
+titlebutton-resize-active
 checkbox-checked-dark
 checkbox-checked-insensitive-dark
 checkbox-unchecked-dark
@@ -60,3 +76,19 @@ switch-header-dark
 switch-active-header-dark
 switch-insensitive-header-dark
 switch-active-insensitive-header-dark
+titlebutton-close-dark
+titlebutton-close-backdrop-dark
+titlebutton-close-hover-dark
+titlebutton-close-active-dark
+titlebutton-max-dark
+titlebutton-max-backdrop-dark
+titlebutton-max-hover-dark
+titlebutton-max-active-dark
+titlebutton-min-dark
+titlebutton-min-backdrop-dark
+titlebutton-min-hover-dark
+titlebutton-min-active-dark
+titlebutton-resize-dark
+titlebutton-resize-backdrop-dark
+titlebutton-resize-hover-dark
+titlebutton-resize-active-dark