Time for a new release

[jekyllbot]

Hello, maintainers! 👋

By my calculations, it's time for a new release of jekyll-sitemap. It's been over 2 months since the last release, v1.4.0.

What else is left to be done before a new release can be made? Please make sure to update History.markdown too if it's not already updated.

Thanks! 💞 ✨