ruby: add page (#1632)

pages/common/ruby.md

@@ -0,0 +1,23 @@
+# ruby
+
+> Ruby programming language interpreter.
+
+- Open an Interactive Ruby Shell (REPL):
+
+`irb`
+
+- Execute a Ruby script:
+
+`ruby {{script.rb}}`
+
+- Execute a single Ruby command in the command line:
+
+`ruby -e {{command}}`
+
+- Check for syntax errors on a given Ruby script:
+
+`ruby -c {{script.rb}}`
+
+- Show the version of Ruby you are using:
+
+`ruby -v`