Scaladoc 3 not linking to sources

[armanbilge]

At least, I can't see where the links are 🧐 Noticed this while looking at:
https://www.javadoc.io/doc/org.typelevel/cats-docs_3/latest/cats/data/Op.html

Note the 2.13 version of the docs has a clear link to the source.
https://www.javadoc.io/doc/org.typelevel/cats-docs_2.13/latest/cats/data/Op.html

This might be an upstream problem, but we should check that we've configured it right before complaining 😅

sbt-typelevel/settings/src/main/scala/org/typelevel/sbt/TypelevelSettingsPlugin.scala

Lines 180 to 181 in b2cabec

	if (tlIsScala3.value)
	Seq("-sourcepath", (LocalRootProject / baseDirectory).value.getAbsolutePath)

Aside: I think this setting should probably be moved to the TypelevelGitHubPlugin in 0.5.0, I don't think it applies in general.

[armanbilge]

Oh, I think we're just missing the setting altogether.

-doc-source-url  Legacy option from Scala 2. Use -source-links instead.
  -source-links  Source links provide a mapping between file in documentation and code repository.

Ok, there are lots of fun settings in there we can enable 😃

                -project  The name of the project.
         -project-footer  A footer on every Scaladoc page.
           -project-logo  Path to the file that contains the project's logo. Provided path can be absolute or relative to the
                          project root directory.
            -project-url  The source repository of your project.
        -project-version  The current version of your project.
               -revision  Revision (branch or ref) used to build project project