doc update structure

docs/howto/include-in-template.md

@@ -0,0 +1,14 @@
+# Include file or template in template
+
+[Jinja2](http://jinja.pocoo.org/docs/2.10/templates/) provides the ability to include an external file/template from within a template with the directive `include`. See the [related doc](http://jinja.pocoo.org/docs/2.10/templates/#include) for more. The path must be relative to the `dotpath`.
+
+For example:
+```yaml
+{%@@ include 'colors/black.colors' @@%}
+```
+
+Of course, paths could be also dynamically generated using variables.
+For example:
+```yaml
+{%@@ include colors_path + '/black.colors' @@%}
+```