feat: add ansible-galaxy metadata

[4censord]

Description

Related to #44

This is a first step for publishing to Ansible galaxy.

It also enabled users to install the collection into their existing ansible projects directly from git.

This can be tested already, using a requirements file like this:

---
collections:
  - name: opensearch.opensearch
    type: git
    source: git+https://github.com/4censord/opensearch-ansible-playbook

or respective ansible-galaxy collection install git+https://github.com/4censord/opensearch-ansible-playbook

Issues Resolved

List any issues this PR will resolve, e.g. Closes [...].

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