expand @ symbols in tokens

refs: #8478

developer/bin/generate_cask_token

@@ -30,6 +30,7 @@ end
 
 EXPANDED_SYMBOLS = {
                     '+' => 'plus',
+                    '@' => 'at',
                    }
 
 CASK_FILE_EXTENSION = '.rb'

doc/cask_token_reference.md

@@ -134,6 +134,7 @@ To convert the App's Simplified Name (above) to a token:
 
   * convert all letters to lower case
   * expand the `+` symbol into a separated English word: `-plus-`
+  * expand the `@` symbol into a separated English word: `-at-`
   * spaces become hyphens
   * hyphens stay hyphens
   * digits stay digits