Release v1.4.0

This is a minor release with some fixes resulting in a few user-facing changes.

• Improve how certain errors raised during dependency installation and load-file checks are shown to the user. Thanks to @sbougerel for raising the issue that lead to this change!
• Use node20 instead of node16, the latter of which is slowly being depreciated in the GitHub Actions ecosystem.
• Change how package-lint-main-file is interpreted for multi-file packages, leading to more intuitive behavior in most cases. Thanks to @chaosemer for raising the issue that lead to this change!
• Disable signature checking while downloading dependencies on old Emacs versions below 27. This was done to work around expired keys distributed with old versions of Emacs, and should be fine for running checks in isolated CI environments. Thanks to @gvol for raising the issue that lead to this change!

I hope this Action will continue to be useful to the Emacs community!