test Scaladoc generation in CI

Author: SethTisue

.github/workflows/ci.yml

@@ -22,4 +22,4 @@ jobs:
         java-version: ${{matrix.java}}
         cache: sbt
     - name: Test
-      run: sbt ++${{matrix.scala}} test package
+      run: sbt ++${{matrix.scala}} test doc package