Support heterogeneous C++26 overloads

[iwubcode]

Would you be interested in updating unordered_dense to support heterogeneous overloads outlined in the paper: cplusplus/papers#1037 (which seems like it is a go for C++26)

It can be helpful when trying to do a find on an object that the map doesn't directly support but can be looked up...but still requiring an insert of the real type if it doesn't exist.

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Contrived example

Today:

ankerl::unordered_dense::map<std::string, int, StringHash, std::equal_to<>> map;
auto it = map.find(std::string_view{"hello world"});
if (it == map.end())
{
  auto [ new_it, success ] = map.emplace(std::string{"hello world"}, 42);
  it = new_it
}
// do something with it

Future:

ankerl::unordered_dense::map<std::string, int, StringHash, std::equal_to<>> map;
auto [ it, success ] = map.try_emplace(std::string_view{"hello world"}, 42);
// do something with it

[martinus]

Hi, certainly sounds like a good idea. Direct link to the API summary of P2364R3: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2363r3.html#summary

[martinus]

Implemented in #36, will create release v1.4.0

[iwubcode]

Thank you so much @martinus !! Really loving your project. Appreciate all the hard work.