Expand Scala tooling coverage

[andrew]

knowledge/scala/ currently detects the language, sbt, ScalaTest, scalafmt, and WartRemover. That misses the second-most-common build tool and most of the test/lint layer, so a Mill or scala-cli project reports Scala-the-language but no package manager, and a MUnit-based project reports no test tool.

Build / package manager

• Mill (https://github.com/com-lihaoyi/mill) — category = "package_manager"; detect build.mill, build.sc, .mill-version; run = "./mill __.compile".
• scala-cli (https://github.com/VirtusLab/scala-cli) — detect project.scala or a *.scala containing //> using; run = "scala-cli compile .".

Test

• MUnit (https://github.com/scalameta/munit) — the default for new Scala 3 projects; detect via "munit" substring in build.sbt / build.mill / build.sc.
• specs2 (https://github.com/etorreborre/specs2) — detect via "specs2" substring.
• utest (https://github.com/com-lihaoyi/utest) — detect via "utest" substring.

Lint

• Scalafix (https://github.com/scalacenter/scalafix) — detect .scalafix.conf.
• Scapegoat (https://github.com/scapegoat-scala/scapegoat) — detect via "scapegoat" in build.sbt / project/plugins.sbt.

sbt detection

• knowledge/scala/sbt.toml detect.files currently matches only the literal build.sbt. Adding "*.sbt" and "project/build.properties" would catch projects that name the root file differently or define the build purely under project/.