fix script to ignore images

scripts/get_external_content.py

@@ -30,6 +30,8 @@ def replace_all_in(folder):
     for root, dirs, files in os.walk(folder):
         for name in files:
             filename = os.path.join(root, name)
+            if filename.endswith(".md"):
+                # only do this on markdown files
                 replace(root, filename)
 
 def replace(folder, filename):