Release v1.6.0

[alancleary]

• Create a branch for the release. release-v1.6.0
• Update the dependencies. The dependabot PR backlog is not comprehensive and doesn't include transitive dependencies, and merging them one at a time tends to break things, so the best way to do this is manually with npm.
• Do a test build of the NPM package on your local machine so you know if something is going off the rails before the automated build action on GitHub.
• Bump the "version" number in package.json and reinstall the dependencies so the correct version number is in package-lock.json.
• Open a PR that merges the release branch into main. PR Release v1.6.0 #410
• Merge the release PR after it passes testing and review.
• Tag a corresponding release on GitHub. This will trigger an automated NPM package build on GitHub. If the package build succeeds it will be automatically published to NPM.