Simpler gallery

- use splide.js
- iterate though a directory automatically

_includes/splide_image.html

@@ -0,0 +1,15 @@
+{% if 'readthedocs.org' in config.docs_dir %}
+{% set assets = '/en/latest/assets' %}
+{% else %}
+{% set assets = '/assets' %}
+{% endif %}
+
+{% if 'http' in src %}
+{% set img_url = src %}
+{% else %}
+{% set img_url = assets  + '/images/' + src %}
+{% endif %}
+
+<li class='splide__slide'>
+    <img src='{{ img_url }}'>
+</li>