Update users-guide-r8.xil

Fixed a typo in my name (which has kept me smiling for years :-), added a link to my github profile and improved the code example for unicode; embedding the font should ensure proper display and i should have included this important detail back then. That's the actual code I still use today in more than a dozen projects!
Merge pull request #39 from manosbatsis/patch-1

Update users-guide-r8.xil