Fix build on Ruby 4.0 (#69)

* Relaxing bundler and rake development dependencies to allow for newer versions

* Add Ruby 4.0 to the test matrix

Author: fnordfish

.github/workflows/ruby.yml

@@ -15,6 +15,7 @@ jobs:
         ruby:
           - 3.3
           - 3.4
+          - 4.0
 
     runs-on: ${{ matrix.os }}-latest
 

argon2.gemspec

@@ -30,9 +30,9 @@ Gem::Specification.new do |spec|
   spec.add_dependency 'ffi', '~> 1.15'
   spec.add_dependency 'ffi-compiler', '~> 1.0'
 
-  spec.add_development_dependency "bundler", '~> 2.0'
+  spec.add_development_dependency "bundler", '>= 2.0'
   spec.add_development_dependency "minitest", '~> 5.8'
-  spec.add_development_dependency "rake", '~> 13.0.1'
+  spec.add_development_dependency "rake", '~> 13.0'
   spec.add_development_dependency "rubocop", '~> 1.7'
   spec.add_development_dependency "simplecov", '~> 0.20'
   spec.add_development_dependency "simplecov-lcov", '~> 0.8'