Switch from webpacker to (css|js)bundling-rails (#227)

* Install jsbundling-rails, uninstall rails/webpacker
* Remove outdated step from run-tests workflow
* Use cssbundling-rails for CSS

Gemfile.lock

@@ -85,6 +85,8 @@ GEM
     concurrent-ruby (1.2.2)
     connection_pool (2.2.5)
     crass (1.0.6)
+    cssbundling-rails (1.1.2)
+      railties (>= 6.0.0)
     date (3.3.3)
     devise (4.7.3)
       bcrypt (~> 3.0)
@@ -113,6 +115,8 @@ GEM
     jbuilder (2.11.5)
       actionview (>= 5.0.0)
       activesupport (>= 5.0.0)
+    jsbundling-rails (1.1.1)
+      railties (>= 6.0.0)
     kaminari (1.2.2)
       activesupport (>= 4.1.0)
       kaminari-actionview (= 1.2.2)
@@ -166,8 +170,6 @@ GEM
       activesupport (>= 3.0.0)
     racc (1.6.2)
     rack (2.2.7)
-    rack-proxy (0.7.6)
-      rack
     rack-test (2.1.0)
       rack (>= 1.3)
     rails (6.1.7.3)
@@ -233,7 +235,6 @@ GEM
       childprocess (>= 0.5, < 5.0)
       rexml (~> 3.2, >= 3.2.5)
       rubyzip (>= 1.2.2)
-    semantic_range (3.0.0)
     spring (2.1.1)
     spring-watcher-listen (2.0.1)
       listen (>= 2.7, < 4.0)
@@ -264,11 +265,6 @@ GEM
       nokogiri (~> 1.6)
       rubyzip (>= 1.3.0)
       selenium-webdriver (~> 4.0)
-    webpacker (5.4.4)
-      activesupport (>= 5.2)
-      rack-proxy (>= 0.6.1)
-      railties (>= 5.2)
-      semantic_range (>= 2.3.0)
     websocket-driver (0.7.5)
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.5)
@@ -283,11 +279,13 @@ DEPENDENCIES
   bootsnap (= 1.12.0)
   byebug
   capybara (= 3.36.0)
+  cssbundling-rails (= 1.1.2)
   devise (= 4.7.3)
   factory_bot_rails (= 5.0.2)
   httparty (= 0.21.0)
   i18n-js (= 3.9.2)
   jbuilder (= 2.11.5)
+  jsbundling-rails (= 1.1.1)
   kaminari (= 1.2.2)
   listen (= 3.5.1)
   pg (= 1.3.5)
@@ -304,7 +302,6 @@ DEPENDENCIES
   tzinfo-data
   web-console (>= 3.3.0)
   webdrivers (= 5.0.0)
-  webpacker (= 5.4.4)
 
 RUBY VERSION
    ruby 3.0.6p216