refactor: allow multi-parent() in Pointer

include/jvalidate/detail/pointer.h

@@ -2,7 +2,6 @@
 
 #include <algorithm>
 #include <cassert>
-#include <cstdint>
 #include <iostream>
 #include <string>
 #include <string_view>
@@ -179,7 +178,7 @@ public:
     return Pointer(std::vector(tokens_.begin() + other.tokens_.size(), tokens_.end()));
   }
 
-  Pointer parent() const { return Pointer({tokens_.begin(), tokens_.end() - 1}); }
+  Pointer parent(size_t i = 1) const { return Pointer({tokens_.begin(), tokens_.end() - i}); }
 
   Pointer & operator/=(Pointer const & relative) {
     tokens_.insert(tokens_.end(), relative.tokens_.begin(), relative.tokens_.end());