ENH: Doxygen use svg and mathjax

Taken from
InsightSoftwareConsortium/ITK@2232191

documentation/Doxygen/doxygen.config.in

@@ -1532,7 +1532,7 @@ MATHJAX_FORMAT         = HTML-CSS
 # The default value is: https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/.
 # This tag requires that the tag USE_MATHJAX is set to YES.
 
-MATHJAX_RELPATH        = http://www.mathjax.org/mathjax
+MATHJAX_RELPATH        = https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.7/
 
 # The MATHJAX_EXTENSIONS tag can be used to specify one or more MathJax
 # extension names that should be enabled during MathJax rendering. For example
@@ -2452,7 +2452,7 @@ DIRECTORY_GRAPH        = YES
 # The default value is: png.
 # This tag requires that the tag HAVE_DOT is set to YES.
 
-DOT_IMAGE_FORMAT       = png
+DOT_IMAGE_FORMAT       = svg
 
 # If DOT_IMAGE_FORMAT is set to svg, then this option can be set to YES to
 # enable generation of interactive SVG images that allow zooming and panning.