Release 2.0.1

[SethTisue]

main motivation: ship #542 which fixes a pretty bad Scala-3-only bug

• merge outstanding PRs
• choose version number
  • 2.0.1
• update crossbuild
  • no changes needed; we're already on 3.0.1 and we dropped 3.0.0-RCx
• create the release and write the notes
  • https://github.com/scala/scala-xml/releases/tag/v2.0.1
• wait for release build
  • https://travis-ci.com/github/scala/scala-xml/builds/233260233/
• release the staging repos
  • https://oss.sonatype.org/#stagingRepositories
• artifacts on Maven Central
  • https://repo1.maven.org/maven2/org/scala-lang/modules/scala-xml_3/2.0.1/
  • https://repo1.maven.org/maven2/org/scala-lang/modules/scala-xml_2.13/2.0.1/
  • https://repo1.maven.org/maven2/org/scala-lang/modules/scala-xml_2.12/2.0.1/
  • (not a complete list)
• post-release, bump version in README and build.sbt
  • 09d527a