add meta/main.yml to be able to use ansible-galaxy

[jybeepeopledoc]

usage example:

# Import nextcloud role
  pre_tasks:
  - name: "get ansible role with ansible-galaxy"
    command: |
      ansible-galaxy install
      --role-file=tools/requirements.yml
      --roles-path="vendor_roles"
      --force

# requirements.yml
---
- name: ReinerNippes.nextcloud
  src: git+git@github.com:ReinerNippes/nextcloud.git
  version: "master"