Add Ruby 3.3 and 3.4 to CI.

- add indirect dev dependency to Gemfile

Author: simi

.github/workflows/ruby.yml

@@ -14,7 +14,7 @@ jobs:
       fail-fast: false
       matrix:
         # Due to https://github.com/actions/runner/issues/849, we have to use quotes for '3.0'
-        ruby: [2.3, 2.4, 2.5, 2.6, 2.7, '3.0', 3.2, truffleruby-head]
+        ruby: [2.3, 2.4, 2.5, 2.6, 2.7, '3.0', 3.2, 3.3, 3.4, truffleruby-head]
 
     steps:
     - uses: actions/checkout@v2

Gemfile

@@ -1,4 +1,6 @@
 source 'https://rubygems.org'
 
+gem 'racc' # needed for outdated spinach gherkin-ruby dependency
+
 # Specify your gem's dependencies in knapsack.gemspec
 gemspec