Prototype of @cfg tag implemented as a class.

lib/jsduck/builtins/cfg.rb

+module JsDuck::Builtins
+  # Implementation of @cfg tag.
+  class Cfg
+    def initialize
+      @pattern = "cfg"
+    end
+
+    def parse(p)
+      p.add_tag(:cfg)
+      p.maybe_type
+      p.maybe_name_with_default
+      maybe_required(p)
+    end
+
+    # matches: "(required)"
+    def maybe_required(p)
+      p.skip_horiz_white
+      if p.look(/\(required\)/i)
+        p.match(/\(required\)/i)
+        p.current_tag[:optional] = false
+      end
+    end
+  end
+end