feat: Support for extending pug templates using relative paths

[sandst1]

Here's another. When extending a Pug template from a relative path, Pug compiler requires a filename attribute to be given in the compile() method options.

<template lang="pug">
  extends ../relative/PugRelativeBase.pug
  block component
    div(class="pug-extended")
</template>

...

pug.compile(templateData, { filename: '/home/user/my/coolest/template/ever.pug' })

Apparently the filename has to be the full path to the file being compiled, which is something that can't be achieved via Jest configuration since it's common to all tests. But as the full path of the file being processed is available in the template compiler, it's easy to pass it to the Pug compiler in order to make extending from relative paths work correctly.

[eddyerburgh]

Thanks again :)