Add keymap and names for F13-F24

[Kaldaien]

We need F13-F15 for our debug functionality in Special K, I was surprised after updating to modern ImGui (from a version ~2018), that F13-F24 aren't even in the new keymap system.

This is a simple fix that adds enumerated values and mapped names for these additional keys. I'd like to see it mainstreamed rather than projects such as NVIDIA Streamline/Reflex that use these infrequently used keys having to modify ImGui code directly.

[PathogenDavid]

Support for these should also be added to the various platform backends.

[ocornut]

Hello,
Thanks for the PR. Yes, it would be good to add support for those keys for all backends where they exist.

[ocornut]

I have merged your commit as 73346e4 + added support in GLFW, SDL2, SDL3, Win32, OSX backends with b0758c8.

[zao]

@ocornut There seems to be a stray (debug?) printf in the win32 implementation:

imgui/backends/imgui_impl_win32.cpp

Line 677 in b0758c8

printf("vk = %X -> key %d, scancode %d\n", vk, key, scancode);

[ocornut]

Amend with 7bbd758