Ignore

Have the build leave the existing yarn lock as is.

This should give the user a chance to manually inspect their yarn.lock file / update it with a command like ./gradlew kotlinUpgradeYarnLock.

This is expected to be a very rarely used strategy. It is provided for users who know what they are doing -- for example, they've manually updated their yarn.lock file on their own, they've removed it from the .gitignore file, they've checked it into source control, and they want to allow their Kobweb site to build despite newer dependencies being available.