Revert "allow custom escape character"

This reverts commit e078efd695.

src/parser.ts

@@ -46,8 +46,7 @@ const parseTokens = (value: string): MaskTokens => {
       pattern: new RegExp(parts[1]),
       optional: parts[2] === 'optional',
       multiple: parts[2] === 'multiple',
-      repeated: parts[2] === 'repeated',
-      escape: parts[2] === 'escape'
+      repeated: parts[2] === 'repeated'
     }
   })