Minor update to 2005/aidan/README.md

Added link to Sudoku. I also learnt that at one point in some places it
was called Number Place so I might've been wrong there. However if
that's indeed true it's not called it now so the statement as it was is
no longer valid nonetheless.

2005/aidan/README.md

@@ -51,7 +51,8 @@ the program as `sudoku-sf.c` which was renamed and changed in their comments.
 
 ## Author's remarks:
 
-This program can solve a type of logic puzzle known as a Sudoku, and also
+This program can solve a type of logic puzzle known as a
+[Sudoku](https://en.wikipedia.org/wiki/Sudoku), and also
 generate new ones.
 
 ### Contents