Postprocess custom output formats

[jmooring]

Hugo cannot convert an SVG to a raster image, nor can it convert a raster image into an SVG.

@jacobtomlinson

if there is a better way to generate og:images with Hugo

Take a look at the theme for the Hugo docs site, specifically:

https://github.com/gohugoio/gohugoioTheme/blob/master/layouts/partials/opengraph/get-featured-image.html

It starts with an empty image, then overlays the desired text.