css_sprite for image tags

reduce number of http requests it makes to fetch image tags by relaying
on a single css sprite image and loading images using stylesheet rules

VRFS-4956

web/Gemfile

@@ -148,6 +148,7 @@ gem 'zip-codes'
 #gem "browserify-rails", "~> 0.7"
 
 gem 'elasticsearch'
+gem 'css_sprite', '~> 2.4'
 
 gem 'logging', '1.7.2'
 

web/Gemfile.lock

@@ -137,6 +137,8 @@ GEM
     concurrent-ruby (1.1.8)
     connection_pool (2.2.3)
     crass (1.0.6)
+    css_sprite (2.4.0)
+      mini_magick
     database_cleaner (1.3.0)
     devise (3.3.0)
       bcrypt (~> 3.0)
@@ -457,6 +459,7 @@ GEM
       mime-types-data (~> 3.2015)
     mime-types-data (3.2021.0212)
     mimemagic (0.3.5)
+    mini_magick (4.11.0)
     mini_mime (1.0.2)
     mini_portile2 (2.4.0)
     minitest (5.14.3)
@@ -810,6 +813,7 @@ DEPENDENCIES
   cause
   coffee-rails
   coffee-script-source (= 1.12.2)
+  css_sprite (~> 2.4)
   database_cleaner (= 1.3.0)
   devise (= 3.3.0)
   elasticsearch