Add Conan package (conan-center-index)

[gistrec]

The library is already available via vcpkg (port geo-utils-cpp).
This issue tracks publishing the library to Conan Center to cover the other half of the C++ ecosystem.

Status

• Open PR to conan-center-index → geo-utils-cpp: new recipe conan-io/conan-center-index#30152
• PR merged
• Update README with Conan installation instructions

References

• vcpkg port: https://github.com/microsoft/vcpkg/tree/master/ports/geo-utils-cpp
• Conan Center contribution guide: https://github.com/conan-io/conan-center-index/blob/master/docs/adding_packages/README.md