gemspec: add base64, bigdecimal

If absent, these gems raise warnings.

Author: olleolleolle

CHANGELOG.md

@@ -10,6 +10,7 @@ Please visit [cucumber/CONTRIBUTING.md](https://github.com/cucumber/cucumber/blo
 
 ## [Unreleased]
 ### Changed
+- Added gems `base64`, `bigdecimal` as dependencies ([olleolleolle](https://github.com/olleolleolle))
 - Updated `cucumber-compatibility-kit` to v16 ([luke-hill](https://github.com/luke-hill))
 - Changed compatibility testing to fully lean on external assets instead of duplicating them ([luke-hill](https://github.com/luke-hill))
 

cucumber.gemspec

@@ -22,6 +22,8 @@ Gem::Specification.new do |s|
   s.required_ruby_version = '>= 3.0'
   s.required_rubygems_version = '>= 3.2.8'
 
+  s.add_dependency 'base64'
+  s.add_dependency 'bigdecimal'
   s.add_dependency 'builder', '~> 3.2'
   s.add_dependency 'cucumber-ci-environment', '> 9', '< 11'
   s.add_dependency 'cucumber-core', '> 13', '< 14'