C++23 support

[heinezen]

Updates nyan to use C++23.

We should wait for openage to implement SFTtech/openage#1787 before we merge this PR.

[Copilot]

Pull Request Overview

This PR updates the nyan project to use C++23 instead of C++20, including updating the CMake configuration, build requirements, and documentation to reflect the new C++ standard.

• Updates CMake build configuration to require C++23 standard
• Updates documentation to specify C++23 compiler requirements with minimum versions
• Reformats README.md tables for better readability while updating technology references

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
nyan/CMakeLists.txt	Changes target compile features from C++17 to C++23
CMakeLists.txt	Updates CMake minimum version and sets C++ standard to 23
doc/building.md	Updates compiler requirements and Ubuntu version for C++23 support
README.md	Updates technology table to show C++23 and improves table formatting

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