define required_ruby_version and metadata

Author: toshimaru

serverkit-vscode.gemspec

@@ -12,6 +12,11 @@ Gem::Specification.new do |spec|
   spec.description   = %q{Serverkit plug-in for VSCode.}
   spec.homepage      = "https://github.com/serverkit/serverkit-vscode"
   spec.license       = "MIT"
+  spec.required_ruby_version = ">= 2.7.0"
+
+  spec.metadata["homepage_uri"] = spec.homepage
+  spec.metadata["source_code_uri"] = "https://github.com/serverkit/serverkit-vscode"
+  spec.metadata["changelog_uri"] = "https://github.com/serverkit/serverkit-vscode/releases"
 
   # Specify which files should be added to the gem when it is released.
   # The `git ls-files -z` loads the files in the RubyGem that have been added into git.