doc: add documentation

Author: meleu

hello_meleu.gemspec

@@ -3,13 +3,14 @@ Gem::Specification.new do |s|
   s.authors = ['meleu']
   s.files = ['lib/hello_meleu.rb']
   s.summary = 'Greeting meleu'
-  s.version = '0.0.2'
+  s.version = '0.0.3'
 
   s.homepage = 'https://github.com/meleu/hello_meleu'
   s.metadata = {
     'bug_tracker_uri' => "#{s.homepage}/issues",
     'changelog_uri' => "#{s.homepage}/releases",
     'wiki_uri' => "#{s.homepage}/wiki",
-    'source_code_uri' => s.homepage
+    'source_code_uri' => s.homepage,
+    'documentation_uri' => 'https://www.rubydoc.info/gems/hello_meleu'
   }
 end

lib/hello_meleu.rb

@@ -1,4 +1,11 @@
+# Class used to greet meleu with "hello".
+#
+# @examples
+# HelloMeleu.hello #=> "Hello meleu!"
 class HelloMeleu
+  # Greets meleu with "hello".
+  #
+  # @return [String] "Hello meleu!"
   def self.hello
     'Hello meleu!'
   end