Add filename filters

[minchinweb]

I.e. start with a filename, and return the file itself, or the just the path.

Ansible has a number of these, that we might be able to just copy.

E.g. for basename --> documentation, implementation.

Their code is under GPL v3+, so this may require changing the repo license.

[minchinweb]

List of all included (Ansible) filters: https://docs.ansible.com/projects/ansible/latest/playbook_guide/playbooks_filters.html#managing-file-names-and-path-names

[minchinweb]

The collection from Ansible appears to have been extracted here --> https://gitlab.com/dreamer-labs/libraries/jinja2-ansible-filters

Last update was ~3 years ago, but I expect the code is mostly static.

It has been published to PyPI as jinja2-ansible-filters.