Add support for Ruby 3.0

GitHub: GH-27

Reported by Herwin. Thanks!!!

Author: kou

.github/workflows/test.yml

@@ -17,9 +17,10 @@ jobs:
           - macos
           - windows
         ruby:
-          - 2.5
-          - 2.6
-          - 2.7
+          - "2.5"
+          - "2.6"
+          - "2.7"
+          - "3.0"
           - head
         include:
           - { os: windows , ruby: mingw }

xmlrpc.gemspec

@@ -20,6 +20,8 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
   spec.required_ruby_version = ">= 2.3"
 
+  spec.add_dependency "webrick"
+
   spec.add_development_dependency "bundler"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "test-unit"