Support config simple template

Can we have some features like this? My case is that I want to provide the theme for others, some templates depend on variables, I hope the user can configure the value with some slot like this:

config.toml:

[extra]
label_title = "{{count}} posts"

template:

<h2>{{ config.extra.label_title | template(attribute=“count",value=“2)”}}</h2>

Any advice?