[Unbundle] Extract img tools into a separate gem plugin (#2984)

switches to using
[`al-img-tools`](https://github.com/al-org-dev/al-img-tools/tree/main)
gem and removes unnecessary code and scripts.

Author: alshedivat

.gitignore

@@ -10,4 +10,4 @@ Gemfile.lock
 assets/libs/
 node_modules/
 vendor
-.idea
+.idea

Gemfile

@@ -42,4 +42,5 @@ group :al_folio_plugins do
     gem 'al_analytics', :git => 'https://github.com/al-org-dev/al-analytics.git'
     gem 'al_citations', :git => 'https://github.com/al-org-dev/al-citations.git'
     gem 'al_ext_posts', :git => 'https://github.com/al-org-dev/al-ext-posts.git'
+    gem 'al_img_tools', :git => 'https://github.com/al-org-dev/al-img-tools.git'
 end