Store example description

src/spectator/dsl.cr

@@ -94,6 +94,10 @@ module Spectator
         def run
           {{block.body}}
         end
+
+        def description
+          {{description.stringify}}
+        end
       end
 
       {% if given_vars.empty? %}

src/spectator/example.cr

@@ -11,6 +11,7 @@ module Spectator
       expect(subject)
     end
 
-    abstract def run
+    abstract def run : Nil
+    abstract def description : String
   end
 end