Add note about documentation status and overall grouping to keyboards…

… too

KeyboardLayouts.md

@@ -1,6 +1,8 @@
 # Keyboard Layouts
 
-Private repositories are not listed.
+Beware that the documentation pages for most Experimental repos have little or no content, and that documentation for other keyboards probably is out-of-date. Writing documentation is an ongoing effort, and part of the development process. Automatically generated SVG layouts is presently not working.
+
+The languages are grouped in three different ways, according to *maturity, geography* and *language family*. [Private repositories](https://github.com/divvun/private-registry) are not listed.
 
 # Grouped according to maturity of the keyboards