Mention the problematic guide in the Readme

README.md

@@ -6,3 +6,10 @@ TODO:
 * Find a way to get the perlin noise inside [-1; 1] or use another noise
 * Add some node which containing items to the simple pyramid "buildings"
 * Change the sky background, fog, etc. in the nether
+* Improve the guide formspec.
+  Writing it in Markdown would be nice.
+  These could be useful:
+  * https://forum.minetest.net/viewtopic.php?t=23855
+    Minetest Bedrock Markup Language
+  * https://github.com/mpeterv/markdown
+    Markdown to HTML converter; Minetest formspecs support HTML