Initial Check in of new Matplotlib Demo

DemoPrograms/Demo_Matplotlib_Two_Windows.py

@@ -0,0 +1,25 @@
+import PySimpleGUI as sg
+import matplotlib.pyplot as plt
+
+"""
+    Simultaneous PySimpleGUI Window AND a Matplotlib Interactive Window
+    A number of people have requested the ability to run a normal PySimpleGUI window that
+    launches a MatplotLib window that is interactive with the usual Matplotlib controls.
+    It turns out to be a rather simple thing to do.  The secret is to add parameter block=False to plt.show()
+"""
+
+
+layout = [[sg.Button('Plot'), sg.Cancel(), sg.Button('Popup')]]
+main_window = sg.Window('Have some Matplotlib....', layout)
+
+while True:
+    event, values = main_window.Read()
+    if event in (None, 'Cancel'):
+        break
+    elif event == 'Plot':
+        history = [0.1, 0.2, 0.5, 0.7]
+        plt.plot(history)
+        plt.show(block=False)
+    elif event == 'Popup':
+        sg.popup('Yes, your application is still running')
+main_window.close()