Add gdzig-zlint with the 0.6.1 ruleset - #3

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, jdx/mise-action@v2. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Unexpected input(s) 'cache_save_post', valid inputs are ['version', 'sha256', 'mise_dir', 'tool_versions', 'mise_toml', 'install', 'install_args', 'install_dir', 'cache', 'cache_save', 'cache_key_prefix', 'experimental', 'log_level', 'working_directory', 'reshim', 'github_token', 'fetch_from_github']