Make dependency on dry-rb gems optional

Author: antstorm

examples/Gemfile

@@ -2,4 +2,7 @@ source 'https://rubygems.org'
 
 gem 'temporal-ruby', path: '../'
 
+gem 'dry-types', '>= 1.2.0'
+gem 'dry-struct', '~> 1.1.1'
+
 gem 'rspec', group: :test

temporal.gemspec

@@ -16,8 +16,6 @@ Gem::Specification.new do |spec|
 
   spec.add_dependency 'grpc'
   spec.add_dependency 'oj'
-  spec.add_dependency 'dry-types', '>= 1.2.0'
-  spec.add_dependency 'dry-struct', '~> 1.1.1'
 
   spec.add_development_dependency 'pry'
   spec.add_development_dependency 'rspec'