Add docs for cson format to menu manager

src/context-menu-manager.coffee

@@ -17,7 +17,7 @@ SpecificityCache = {}
 # An instance of this class is always available as the `atom.contextMenu`
 # global.
 #
-# ## Format
+# ## Context Menu CSON Format
 #
 # # ```coffee
 # 'atom-workspace': [{label: 'Help', command: 'application:open-documentation'}]

src/menu-manager.coffee

@@ -12,6 +12,49 @@ MenuHelpers = require './menu-helpers'
 # application menu.
 #
 # An instance of this class is always available as the `atom.menu` global.
+#
+# ## Menu CSON Format
+#
+# Here is an example from the [tree-view](https://github.com/atom/tree-view/blob/master/menus/tree-view.cson):
+#
+# ```coffee
+# [
+#   {
+#     'label': 'View'
+#     'submenu': [
+#       { 'label': 'Toggle Tree View', 'command': 'tree-view:toggle' }
+#     ]
+#   }
+#   {
+#     'label': 'Packages'
+#     'submenu': [
+#       'label': 'Tree View'
+#       'submenu': [
+#         { 'label': 'Focus', 'command': 'tree-view:toggle-focus' }
+#         { 'label': 'Toggle', 'command': 'tree-view:toggle' }
+#         { 'label': 'Reveal Active File', 'command': 'tree-view:reveal-active-file' }
+#         { 'label': 'Toggle Tree Side', 'command': 'tree-view:toggle-side' }
+#       ]
+#     ]
+#   }
+# ]
+# ```
+#
+# Use in your package's menu `.cson` file requires that you place your menu
+# structure under a `menu` key.
+#
+# ```coffee
+# 'menu': [
+#   {
+#     'label': 'View'
+#     'submenu': [
+#       { 'label': 'Toggle Tree View', 'command': 'tree-view:toggle' }
+#     ]
+#   }
+# ]
+# ```
+#
+# See {::add} for more info about adding menu's directly.
 module.exports =
 class MenuManager
   constructor: ({@resourcePath}) ->