Lab 3B submission guidelines

[Jannis Limperg]

Hej,

for lab 3A, there were a number of submissions where the automatic
checks got tripped up by trivial formalities. This is a little annoying
because we then have to download your submission, fix it and run it
through the testsuite manually. Therefore, please make sure to observe
the following:

- Your submitted file should be called exactly `Sudoku.hs`.
- Your submitted file should start with the line
`module Sudoku where`.
- Your `Sudoku` type should have `Eq` and `Show` instances. You can
derive these:

data Sudoku = ...
deriving (Eq, Show)

If you use the template from the lab text [1], you should be good.

These are guidelines, not requirements, so we won't reject your
submission if you don't observe them. But please do anyway. ;)

Cheers,
Jannis

[1] http://www.cse.chalmers.se/edu/year/2018/course/TDA452/labs/3/Sudoku.hs