Custom py script for jinja2 rendering

[queria]

As alternative to currently j2cli or such feature-full/heavy tool, small custom python script is enough for rendering jinja2 templates.

Closes #77

[queria]

This is example of how j2cli or such tool can be replaced with custom (small) script.

I of course understand if usage of j2 or alternative is desired (as they can be provide many more useful features), so just reject/close this in that case please, no need for explaining.