added GTK4 support

examples/builder.nim

@@ -1,31 +0,0 @@
-# https://developer.gnome.org/gtk3/stable/ch01s03.html
-# builder.nim -- application style example using builder/glade xml file for user interface
-# nim c builder.nim
-import gintro/[gtk, glib, gobject, gio]
-
-proc hello(b: Button; msg: string) =
-  echo "Hello", msg
-
-proc quitApp(b: Button; app: Application) =
-  echo "Bye"
-  quit(app)
-
-proc appActivate(app: Application) =
-  let builder = newBuilder()
-  discard builder.addFromFile("builder.ui")
-  let window = builder.getApplicationWindow("window")
-  window.setApplication(app)
-  var button = builder.getButton("button1")
-  button.connect("clicked", hello, "")
-  button = builder.getButton("button2")
-  button.connect("clicked", hello, " again...")
-  button = builder.getButton("quit")
-  button.connect("clicked", quitApp, app)
-  #showAll(window)
-
-proc main =
-  let app = newApplication("org.gtk.example")
-  connect(app, "activate", appActivate)
-  discard run(app)
-
-main()