Add example; Fix example in README

README.md

@@ -20,7 +20,7 @@ run(
 Dust can do amazing things with data. To load CSV data, isolate a column and render it as a line plot in a GUI window:
 
 ```dust
-read("examples/assets/faithful.csv")
+read_file("examples/assets/faithful.csv")
     -> from_csv(input)
     -> rows(input)
     -> transform(input, 'input.1')

examples/gui_rendering.ds

@@ -0,0 +1,6 @@
+# This will read a CSV file and display it as a line plot in a GUI window.
+read_file("examples/assets/faithful.csv")
+    -> from_csv(input)
+    -> rows(input)
+    -> transform(input, 'input.1')
+    -> plot(input);