devel/rubygem-gyoku: update to 1.4.0 and take maintainership

While here:

• Updated PORTVERSION to DISTVERSION
• Added rubygem-rexml, which prevents build failure
• Formatted the Makefile
• Added more description about the port

Changelog: https://github.com/savonrb/gyoku/blob/v1.4.0/CHANGELOG.md

PR: 288447
Reported by: Atanu Biswas <atanubiswas484@gmail.com> (new maintainer)