Include short-code to embed SVG images

Including SVG images using standard markdown disables certain features.
This commit adds a short-code that allows embedding SVG images. By
embedding the SVG image, its features are retained.
SVG features include clickable linked areas, hover texts, etc.

Usage example:
{{< svg "/images/example.svg" >}}

Signed-off-by: Sietze van Buuren <Sietze.vanBuuren@de.bosch.com>

themes/apertis/layouts/shortcodes/svg.html

+<figure style="text-align: center;">
+    {{ readFile (print "static" (index .Params 0)) | safeHTML }}
+</figure>
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