Added file property example

Author: manuelkoester

NodeGraphQt/custom_widgets/properties_bin/node_property_widgets.py

@@ -565,6 +565,11 @@ def __init__(self):
                 value='text edit test',
                 widget_type=NodePropWidgetEnum.QLABEL.value
             )
+            self.create_property(
+                "file",
+                value="",
+                widget_type=NodePropWidgetEnum.FILE_OPEN.value
+            )
             self.create_property(
                 'color_picker',
                 value=(0, 0, 255),