Load presets from front matter + allow both bundled and global bergamot files

Signed-off-by: Danila Fedorin <danila.fedorin@gmail.com>

layouts/partials/bergamotrenderpreset.html

@@ -1,6 +1,6 @@
 <script>
     window.addEventListener('load', function() {
         window.Bergamot.renderPresets['{{ .name }}'] =
-            {{ readFile (printf "static/bergamot/rendering/%s" .file) }};
+            {{ .file }};
     });
 </script>