Add homepage and source code URIs to gemspec metadata

Author: ydah

racc.gemspec

@@ -44,6 +44,8 @@ DESC
   s.required_ruby_version = ">= 2.5"
   s.rdoc_options = ["--main", "README.rdoc"]
   s.extra_rdoc_files = ["README.ja.rdoc", "README.rdoc"]
+  s.metadata["homepage_uri"] = s.homepage
+  s.metadata["source_code_uri"] = s.homepage
   s.metadata["changelog_uri"] = "#{s.homepage}/releases"
 
   if RUBY_PLATFORM =~ /java/