sbt warning about unused setting `docs / previewSite / previewPath`

Running sbt shows the following warning each time: ``` [warn] there's a key that's not used by any other settings/tasks: [warn] [warn] * docs / previewSite / previewPath [warn] +- /home/runner/work/pekko-persistence-r2dbc/pekko-persistence-r2dbc/build.sbt:94 [warn] [warn] note: a setting might still be used by a command; to exclude a key from this `lintUnused` check [warn] either append it to `Global / excludeLintKeys` or call .withRank(KeyRanks.Invisible) on the key ``` I think this is because about a year ago `SitePreviewPlugin` was changed to no longer automatically enable on modules that have other `sbt-site` plugins added - https://github.com/sbt/sbt-site/blame/601922e00a77753d950a0b7afce83f514fafd180/core/src/main/scala/com/typesafe/sbt/site/SitePreviewPlugin.scala#L10. Would it be okay to add `SitePreviewPlugin` to `docs` module, or should we remove the setting? Seems to me that having the plugin enabled would be helpful, or at the very least harmless.