Added files required to enable USB CD drive on the TinyLlama2 board

[sandlbn]

I am adding the files required to enable USB CD drives on the TinyLlama board. As GitHub doesn't allow opening PR against wiki, please copy content from https://github.com/sandlbn/tinyllama2/wiki. One file need to be copied USB-CD-ROM.md and one line from _Sidebar.md.

[eivindbohler]

Thanks for testing the USB cd-rom drive! :) I can add a few lines about that in the wiki, sure! As for the drivers, mscdex.exe is already included in MS-DOS 6.22 (and on the virtual floppy). I think it would be better to add a link to where you found the other two sys files and what exactly they support instead of including them directly in this repo.