Include listings package and uncomment Finnish code example - Allows the inclusion of code snippets via the command `\lstinputlisting`. This command is absolutely required, if the code or its comments contain special Unicode characters. - The package is loaded in `preamble.tex`. - The Finnish listing example was uncommented in `tex/esitystyyli.tex`, made possible by instructing `listings` to convert special characters to equivalent LaTeΧ commands in the preamble.