Prep for release: update version and history

[zkoppert]

This pull request introduces version 5.0.2 of the library, which includes dependency updates, a change in Ruby version support, and a version bump in the codebase. Below are the most important changes grouped by theme:

Version and compatibility updates:

• Updated the version in lib/github-markup.rb from 5.0.1 to 5.0.2.
• Dropped support for Ruby versions below 3.1.

Dependency updates:

• Updated multiple dependencies in HISTORY.md, including nokogiri, rdoc, activesupport, sanitize, and others, to their respective newer versions.
• Updated the commonmarker dependency to use a Git tag for version v0.18.3.
• Updated the racc dependency within nokogiri to ~> 1.4.
• Changed the dependency source URL to use HTTPS for improved security.

[Copilot]

Pull Request Overview

This PR prepares the github-markup library for a 5.0.2 release by updating the version number and documenting changes in the release history. The changes focus on dependency updates and Ruby version support modifications.

• Updated library version from 5.0.1 to 5.0.2
• Added comprehensive release notes documenting dependency updates and Ruby version support changes
• Documented the drop of support for Ruby versions below 3.1

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
lib/github-markup.rb	Updates the VERSION constant from '5.0.1' to '5.0.2'
HISTORY.md	Adds release notes for version 5.0.2 with detailed dependency updates and Ruby version changes