format Makefile

Author: Vladimir Kotal

README.md

@@ -4,6 +4,6 @@ This project contains source code for the material that is used to lecture "Unix
 Programming in C" (NSWI015) class at the Faculty of Mathematics and Physics,
 Charles University in Prague.
 
-It is written in LaTeX.  See the Makefile on how to build the PDF document.
+It is written in LaTeX.  See the `Makefile` on how to build the PDF document.
 
 The class home page is https://devnull-cz.github.io/unix-linux-prog-in-c/