adding alignment example

Author: FoamyGuy

examples/images/blue_rectangle.bmp

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+# SPDX-FileCopyrightText: 2020 Foamyguy
+#
+# SPDX-License-Identifier: Unlicense

examples/images/blue_rectangle.bmp.license

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+# SPDX-FileCopyrightText: 2020 Foamyguy
+#
+# SPDX-License-Identifier: Unlicense

examples/images/green_circle.bmp

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+# SPDX-FileCopyrightText: 2020 Foamyguy
+#
+# SPDX-License-Identifier: Unlicense

examples/images/green_circle.bmp.license

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+# SPDX-FileCopyrightText: 2020 Foamyguy
+#
+# SPDX-License-Identifier: Unlicense

examples/images/purple_oval.bmp

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+"""
+This example runs best on a PyPortal or other device with a
+display larger than 128px in both directions.
+
+This example cycles through 4 different images and moves
+them around to different positions on the screen each
+time it updates by using the alignment feature.
+"""
+import board
+from adafruit_slideshow import (
+    PlayBackOrder,
+    SlideShow,
+    VerticalAlignment,
+    HorizontalAlignment,
+)
+
+# pylint: disable=no-member
+
+# Create the slideshow object that plays through once alphabetically.
+slideshow = SlideShow(
+    board.DISPLAY, None, folder="/images/", loop=True, order=PlayBackOrder.ALPHABETICAL,
+)
+
+aligns = [
+    (VerticalAlignment.TOP, HorizontalAlignment.CENTER),
+    (VerticalAlignment.TOP, HorizontalAlignment.RIGHT),
+    (VerticalAlignment.CENTER, HorizontalAlignment.LEFT),
+    (VerticalAlignment.CENTER, HorizontalAlignment.CENTER),
+    (VerticalAlignment.CENTER, HorizontalAlignment.RIGHT),
+    (VerticalAlignment.BOTTOM, HorizontalAlignment.LEFT),
+    (VerticalAlignment.BOTTOM, HorizontalAlignment.CENTER),
+    (VerticalAlignment.BOTTOM, HorizontalAlignment.RIGHT),
+    (VerticalAlignment.TOP, HorizontalAlignment.LEFT),
+]
+i = 0
+slideshow.h_align = aligns[i][1]
+slideshow.v_align = aligns[i][0]
+i += 1
+
+prev_img = slideshow.current_image_name
+while slideshow.update():
+    cur_img = slideshow.current_image_name
+    if prev_img != cur_img:
+        slideshow.h_align = aligns[i][1]
+        slideshow.v_align = aligns[i][0]
+        i += 1
+        if i >= len(aligns):
+            i = 0
+
+    prev_img = cur_img