New demo that shows how to use new spinner change submits capability

Demo_Font_Sizer.py

@@ -0,0 +1,28 @@
+
+# Testing async form, see if can have a spinner
+# that adjusts the size of text displayed
+
+import PySimpleGUI as sg
+
+form = sg.FlexForm("Font size selector")
+
+fontSize = 12
+sampleText = sg.Text("Aa", size=(2, 1), font="Helvetica " + str(fontSize))
+layout = [
+          [sampleText, sg.Spin([sz for sz in range(4,72)], font=('Helvetica 20'), initial_value=fontSize, change_submits=True, key='spin')],
+          [sg.OK(), sg.Cancel()]
+         ]
+
+sz = fontSize
+form.Layout(layout)
+while True:
+    button, values= form.Read()
+    if button is None:
+        break
+    sz = int(values['spin'])
+    if sz != fontSize:
+        fontSize = sz
+        font = "Helvetica " + str(fontSize)
+        sampleText.Update(font=font)
+
+print("Done.")