Add example image for alt text

Author: reknih

NOTICE

@@ -495,6 +495,11 @@ The Creative Commons Attribution 4.0 International License applies to:
   (https://github.com/karlrupp/microprocessor-trend-data, https://ourworldindata.org/grapher/transistors-per-microprocessor)
   Years 1971-1994 deleted
 
+* "Reiher im Flug" in files/images/heron.jpg
+  Copyright 2023 Makasch1966
+  Via Wikimedia Commons
+  (https://commons.wikimedia.org/wiki/File:Reiher_im_Flug.jpg)
+
 Attribution 4.0 International
 
 =======================================================================

files/images/heron.jpg

@@ -107,6 +107,7 @@ files! {
     "images/f2t.jpg",
     "images/glacier.jpg",
     "images/graph.png",
+    "images/heron.jpg",
     "images/linked.svg",
     "images/logo.svg",
     "images/matplotlib.pdf",