readme: added optional pkgs

README.md

@@ -4,6 +4,8 @@
 
 ```sh
 sudo apt-get install latexmk zathura
+# optional:
+sudo apt-get install texlive-latex-extra texlive-science biber
 git clone git@git.hammerle.me:fphammerle/config-latexmk.git ~/.config/latexmk
 ln --symbolic --backup=numbered .config/latexmk/latexmkrc ~/.latexmkrc
 ```