CI: Add an out of range palette test image.

Tests for #227

Author: Gadgetoid

tests/test_e673.py

@@ -0,0 +1,12 @@
+def test_set_image_p256(GPIO, spidev):
+    from inky import inky_e673
+    from PIL import Image
+
+    img = Image.new("P", (800, 480))
+
+    for x in range(256):
+        img.putpixel((x, x), (x, 0, 0))
+
+    inky = inky_e673.Inky()
+
+    inky.set_image(img)