devel/semver: Add port: Semantic Versioning for modern C++

semver is a header-only semantic versioning library for modern C++. It
allows to compare and manipulate versions complying with the Semantic
Versioning 2.0.0 specification. It is licensed under the MIT License.

WWW: https://github.com/Neargye/semver

PR: 290206
Reported by: Stefan Schlosser <bsdcode@disroot.org> (new maintainer)