what is a .pug file code example

Example 1: what is pug template engine

Pug is a template engine for Node and for the browser. 
It compiles to HTML and has a simplified syntax, which 
can make you more productive and your code more readable.
Pug makes it easy both to write reusable HTML, as well as
to render data pulled from a database or API.

Example 2: pug templates includes

//- index.pug, Including Filtered text
doctype html
html
  head
    title An Article
  body
    include:markdown-it article.md