web: Add "resources" template

Quite a few of the pages have a resources -section with data-sheet
and/or product page. Having a template for this section can reduce
copy-paste a bit, keeps the outlook of the pages coherent, and can
potentially help avoid mistakes.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>

Author: M-Vaittinen

_includes/resources.md

@@ -0,0 +1,8 @@
+## Resources
+{%- if page.datasheet %}
+- [Datasheet]({{ page.datasheet }})
+{%- endif %}
+{%- if page.productpage %}
+- [Product Page]({{ page.productpage }})
+{%- endif %}
+