🐛 Fix string_view construction

Problem:
- `string_view`'s constructor takes a `char const *` and a size, not an iterator
  and a size. On platforms where an array iterator is not a simple pointer, this
  fails.

Solution:
- Use `data` instead of `cbegin` to access the string data.

Author: elbeno

include/stdx/ct_string.hpp

@@ -52,7 +52,7 @@ template <std::size_t N> struct ct_string {
     constexpr static std::integral_constant<bool, N == 1U> empty{};
 
     constexpr explicit(true) operator std::string_view() const {
-        return std::string_view{value.cbegin(), size()};
+        return std::string_view{value.data(), size()};
     }
 
     std::array<char, N> value{};