Add ImageMagick, ghostscript, bc_math and PDF thumbnails

[joshuafredrickson]

Addresses #1108

[swalkinshaw]

Thank you 🎉 tested and site health all passes

[strarsis]

What about adding the PHP SOAP extension? Some plugins for WooCommerce use/need it. You may find this PHP extensions table interesting: https://github.com/strarsis/docker-php-bedrock/blob/main/README.md#php-extensions

Edit: Would this config be better for imagemagick PDF configuration as it is imagemagick version-agnostic?

# ImageMagick fix (allow reading PDFs)
# https://alexvanderbist.com/posts/2018/fixing-imagick-error-unauthorized
- name: Find ImageMagick directories
  find:
    paths: /etc
    pattern: "ImageMagick(?:-\\d)"
    file_type: directory
    use_regex: yes
  register: imagemagick_directories

- name: Allow ImageMagick coder to read and write
  lineinfile:
    dest: "{{ item.path }}/policy.xml"
    regexp: '\s*<policy domain="coder" rights="none" pattern="PDF" />'
    line: '  <policy domain="coder" rights="read|write" pattern="PDF" />'
    backrefs: yes
  with_items: "{{ imagemagick_directories.files }}"
  notify: reload php-fpm

[strarsis]

@joshuafredrickson: Pardon my ignorance, but I can't find where in this PR the bc_math PHP extension is added. 😼