Added svgo for svg optimization
Added svgo for svg optimization

With default options it varies from ~30% reduction for plantuml
generated, all the way up to 80 to 90 precent for inkscape based
images.

wilsonfreitas/pelican-plugins,UHBiocomputation/pelican-plugins,MarkusH/pelican-plugins,mortada/pelican-plugins,howthebodyworks/pelican-plugins,talha131/pelican-plugins,UHBiocomputation/pelican-plugins,mortada/pelican-plugins,xsteadfastx/pelican-plugins,mortada/pelican-plugins,mikitex70/pelican-plugins,mikitex70/pelican-plugins,howthebodyworks/pelican-plugins,rlaboiss/pelican-plugins,wilsonfreitas/pelican-plugins,rlaboiss/pelican-plugins,xsteadfastx/pelican-plugins,xsteadfastx/pelican-plugins,danmackinlay/pelican-plugins,mortada/pelican-plugins,talha131/pelican-plugins,MarkusH/pelican-plugins,mikitex70/pelican-plugins,danmackinlay/pelican-plugins,mikitex70/pelican-plugins,rlaboiss/pelican-plugins,danmackinlay/pelican-plugins,howthebodyworks/pelican-plugins,rlaboiss/pelican-plugins,danmackinlay/pelican-plugins,MarkusH/pelican-plugins,UHBiocomputation/pelican-plugins,wilsonfreitas/pelican-plugins,UHBiocomputation/pelican-plugins,talha131/pelican-plugins,howthebodyworks/pelican-plugins,MarkusH/pelican-plugins,wilsonfreitas/pelican-plugins,talha131/pelican-plugins,talha131/pelican-plugins,MarkusH/pelican-plugins,mortada/pelican-plugins,xsteadfastx/pelican-plugins