Roll a release (2.2.0)

[SethTisue]

because we want to ship #496, to aid people migrating from Scala 2.12 to 2.13 (2.13 is much better at issuing exhaustiveness warnings than 2.12 was, so the lack of an irrefutable extractor is especially likely to bite upgraders)

cc @lrytz

[SethTisue]

• tag https://github.com/scala/scala-parser-combinators/releases/tag/v2.2.0
• release build https://github.com/scala/scala-parser-combinators/actions/runs/4019588896
• artifacts on Maven Central https://repo1.maven.org/maven2/org/scala-lang/modules/scala-parser-combinators_3/2.2.0/

[SethTisue]

sonatype is sloooooowwww today