A thumbnail may be mandatory (#5077)

diff --git a/cc-by-sa/knowledge/modules/introducing_type/lessons/introducing_color_fonts/images/thumbnail.svg b/cc-by-sa/knowledge/modules/introducing_type/lessons/introducing_color_fonts/images/thumbnail.svg
new file mode 100644 (file)
index 0000000..0926d4f
--- /dev/null
+++ b/cc-by-sa/knowledge/modules/introducing_type/lessons/introducing_color_fonts/images/thumbnail.svg
@@ -0,0 +1,3 @@
+<svg width="1920" height="1080" fill="none" xmlns="http://www.w3.org/2000/svg">
+<!-- TODO: a real thumbnail -->
+</svg>
\ No newline at end of file