Convert gif inside PDF build process to PNGs

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

user_manual/conf.py

@@ -183,7 +183,10 @@ latex_elements = {
 #'pointsize': '10pt',
 
 # Additional stuff for the LaTeX preamble.
-#'preamble': '',
+'preamble': '\usepackage{epstopdf}\
+\
+\epstopdfDeclareGraphicsRule{.gif}{png}{.png}{convert gif:#1 png:\OutputFile}\
+\AppendGraphicsExtensions{.gif}',
 }
 
 # Grouping the document tree into LaTeX files. List of tuples