Update README.md, add limitations

README.md

@@ -92,7 +92,7 @@ When storing a CTF challenge with ctfstore.py a docker-compose.yml file is expec
 
 ### OS - custom kernel:
 * Debian stable (i386 and x86_64) (ssh access for user "ctf")
-* Linux kernel (5.x, 4.x, 3.x)
+* Linux kernel (5.x, 4.x, 3.x) (see [limitations](exploitdb/ctfsetup/qemu/Readme.md))
 
 ### Other:
 * Empty Dockerfile and docker-compose.yml