Add `imagemagick` package

[yahonda]

This commit addresses the "MiniMagick::Invalid: You must have ImageMagick or GraphicsMagick installed" error.

• Steps to reproduce

  vagrant ssh
  git clone https://github.com/rails/rails
  cd rails
  bundle install
  cd activestorage
  bin/test test/models/representation_test.rb -n test_representing_an_image

• This commit addresses the following error:

  
  $ bin/test test/models/representation_test.rb -n test_representing_an_image
  ... snip ...
  E

Error: ActiveStorage::RepresentationTest#test_representing_an_image: MiniMagick::Invalid: You must have ImageMagick or GraphicsMagick installed /var/lib/gems/3.1.0/gems/mini_magick-4.12.0/lib/mini_magick/image.rb:221:in rescue in validate!' /var/lib/gems/3.1.0/gems/mini_magick-4.12.0/lib/mini_magick/image.rb:218:invalidate!' /var/lib/gems/3.1.0/gems/mini_magick-4.12.0/lib/mini_magick/image.rb:131:in `block in create'

:90:in `tap' /var/lib/gems/3.1.0/gems/mini_magick-4.12.0/lib/mini_magick/image.rb:130:in `create' /var/lib/gems/3.1.0/gems/mini_magick-4.12.0/lib/mini_magick/image.rb:34:in `read' /var/lib/gems/3.1.0/gems/mini_magick-4.12.0/lib/mini_magick/image.rb:108:in `block in open' /var/lib/gems/3.1.0/gems/mini_magick-4.12.0/lib/mini_magick/image.rb:108:in `open' /var/lib/gems/3.1.0/gems/mini_magick-4.12.0/lib/mini_magick/image.rb:108:in `open' /var/lib/gems/3.1.0/gems/mini_magick-4.12.0/lib/mini_magick/image.rb:108:in `open' /home/vagrant/rails/activestorage/test/test_helper.rb:70:in `read_image' /home/vagrant/rails/activestorage/test/models/representation_test.rb:11:in `block in ' bin/test test/models/representation_test.rb:7 Finished in 0.472072s, 2.1183 runs/s, 0.0000 assertions/s. 1 runs, 0 assertions, 0 failures, 1 errors, 0 skips $ ```