feat(ruby-client): 新增 Ruby 客户端 SDK 及 demo，移除 C 语言支持

- 新增 kenaito-conf-ruby-client（Ruby 2.5+）及对应 demo
- 新增 Dockerfile.ruby
- README 技术栈移除 C，项目结构补充 Ruby 客户端
- README_EN.md 同步更新
- README_DOCKERFILE.md 补充 Ruby 构建命令

kenaito-conf-ruby-client/kenaito-conf.gemspec

@@ -0,0 +1,17 @@
+Gem::Specification.new do |spec|
+  spec.name          = 'kenaito-conf'
+  spec.version       = '1.0.3'
+  spec.authors       = ['odboy']
+  spec.email         = ['odboy@outlook.com']
+
+  spec.summary       = 'Kenaito Config Center Ruby Client'
+  spec.description   = 'Ruby client SDK for Kenaito Config Center'
+  spec.homepage      = 'https://github.com/odboy/kenaito-conf'
+  spec.license       = 'Apache-2.0'
+  spec.required_ruby_version = '>= 2.5.0'
+
+  spec.files         = Dir['lib/**/*.rb']
+  spec.require_paths = ['lib']
+
+  spec.add_development_dependency 'rake', '~> 13.0'
+end