Add Rake.

rake.md

@@ -0,0 +1,34 @@
+---
+title: Rake
+layout: default
+---
+
+### Basic syntax
+
+```rb
+namespace :foo do
+  desc "Description"
+  task :bar do
+    ...
+  end
+
+  task :baz => :dependency do
+  end
+
+  task :baz => [:dep1, :dep2, dep3] do
+  end
+end
+
+# rake foo:bar
+```
+
+### Rake task with arguments
+
+```rb
+desc "Do something"
+task :workit, [:id] => :environment do |_, args|
+  id = args[:id]
+end
+
+# rake workit[234]
+```