Switch from Webpacker to cssbundling-rails, upgrade Tailwind

Gemfile.lock

@@ -79,6 +79,8 @@ GEM
     crack (0.4.5)
       rexml
     crass (1.0.6)
+    cssbundling-rails (1.0.0)
+      railties (>= 6.0.0)
     database_cleaner (2.0.1)
       database_cleaner-active_record (~> 2.0.0)
     database_cleaner-active_record (2.0.1)
@@ -159,11 +161,15 @@ GEM
     matrix (0.4.2)
     method_source (1.0.0)
     mini_mime (1.1.2)
+    mini_portile2 (2.6.1)
     minitest (5.14.4)
     msgpack (1.4.2)
     multipart-post (2.1.1)
     net-ldap (0.17.0)
     nio4r (2.5.8)
+    nokogiri (1.12.5)
+      mini_portile2 (~> 2.6.1)
+      racc (~> 1.4)
     nokogiri (1.12.5-x86_64-linux)
       racc (~> 1.4)
     orm_adapter (0.5.0)
@@ -174,8 +180,6 @@ GEM
     raabro (1.4.0)
     racc (1.6.0)
     rack (2.2.3)
-    rack-proxy (0.7.0)
-      rack
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
     rails (6.0.4.1)
@@ -292,10 +296,6 @@ GEM
       addressable (>= 2.8.0)
       crack (>= 0.3.2)
       hashdiff (>= 0.4.0, < 2.0.0)
-    webpacker (4.3.0)
-      activesupport (>= 4.2)
-      rack-proxy (>= 0.6.1)
-      railties (>= 4.2)
     websocket-driver (0.7.5)
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.5)
@@ -311,6 +311,7 @@ DEPENDENCIES
   bootsnap (>= 1.4.2)
   byebug
   capybara
+  cssbundling-rails
   database_cleaner
   devise
   devise_ldap_authenticatable
@@ -339,7 +340,6 @@ DEPENDENCIES
   warden
   web-console (>= 3.3.0)
   webmock
-  webpacker (~> 4.0)
 
 BUNDLED WITH
-   2.2.2
+   2.3.6