Change Documentation graphics from PNG to SVG format

Changes the generated images from PNG to SVG for size and better rendering on most browsers, and in
the generated epub and pdf documents.

Signed-off-by: Winford <winford@object.stream>

Author: UncleGrumpy

doc/Doxyfile.in

@@ -2304,7 +2304,7 @@ 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.

doc/conf.py.in

@@ -60,6 +60,7 @@ extensions = [
     'sphinx.ext.graphviz'
 ]
 
+
 suppress_warnings = [
     'epub.unknown_project_files',
     'misc.highlighting_failure',
@@ -90,6 +91,8 @@ source_suffix = {
 
 # -- Sphinx Extension configuration ---------------------------------------------------
 
+graphviz_output_format = 'svg'
+
 # Breathe configuration
 breathe_projects = { "libatomvm": "@CMAKE_CURRENT_BINARY_DIR@/xml/" }
 breathe_default_project = "libatomvm"