Ensure that translations are updated after every commit to lektor branch

[freakboy3742]

CI will re-publish the website on every commit to the lektor branch. However, there's no guarantee that the translation file is up to date. This PR changes the publish workflow so that:

• If a change is made to a non-translatable file (e.g., a blog post), CI will publish immediately.
• If a change is made to a translatable file, CI will do a build. If this results in any changes to the i18n directory, those changes will be committed, and the publication pass will be aborted.
• However, this will be new commit to the lektor branch, which will trigger a new build. This new build should result in no change to the translation files, so the publication can continue.

This requires an update to the lektor-i18n plugin to ensure that the creation date in the POT file isn't updated on every build.

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct