Upgrade development Node.js LTS and dependent packages to the latest version

[yhatt]

Notable changes

• Node.js LTS for development has been bumped from v20 to v22.
• Marpit is updated to v3.1.2. (Bump @marp-team/marpit from 3.1.1 to 3.1.2 #390)
• Fixed reported vulnerabilties in dependencies.
• Deal with Sass deprecation warnings about the usage of @import.
  • Replace to use meta.load-css() and pkg:, the package importer.
    • https://sass-lang.com/blog/import-is-deprecated/
    • https://sass-lang.com/blog/announcing-pkg-importers/
  • sass-extended-importer dev dependency is no longer required.
• github-markdown-css has been locked into the latest version v5.8.1.
  • The style of this version is using rem unit for spacing. This change may break existing slide layouts, so spacing variables have been overloaded by using previous px unit.