Update sbt-unidoc to 0.6.0

Author: 47erbot

project/plugins.sbt

@@ -2,7 +2,7 @@ addSbtPlugin("com.github.sbt"      % "sbt-ci-release"           % "1.6.0")
 addSbtPlugin("com.47deg"           % "sbt-microsites"           % "1.4.4")
 addSbtPlugin("org.scalameta"       % "sbt-scalafmt"             % "2.5.5")
 addSbtPlugin("org.scalameta"       % "sbt-mdoc"                 % "2.7.2")
-addSbtPlugin("com.github.sbt"      % "sbt-unidoc"               % "0.5.0")
+addSbtPlugin("com.github.sbt"      % "sbt-unidoc"               % "0.6.0")
 addSbtPlugin("de.heikoseeberger"   % "sbt-header"               % "5.10.0")
 addSbtPlugin("com.alejandrohdezma" % "sbt-github"               % "0.12.0")
 addSbtPlugin("com.alejandrohdezma" % "sbt-github-header"        % "0.12.0")