v2.1.0: more combinators, cats/cats-effect 2.3.0

What’s Changed

• Update scalafmt to 2.7.5 (#262) @etspaceman
• Rename retryingM to retryingOnFailures (#261) @etspaceman
• Improve combinators documentation (#264) @cb372
• Functionality to Retry Failures and Errors In The Same Retry Strategy (#259) @etspaceman
• Update sbt-ci-release to 1.5.5 (#257) @scala-steward
• Update cats-core to 2.3.0 (#263) @etspaceman
• Update sbt to 1.4.5 (#260) @scala-steward
• Update cats-effect to 2.3.0 (#254) @scala-steward
• Update cats-mtl to 1.1.0 (#253) @scala-steward
• Update sbt-scalajs, scalajs-compiler, ... to 1.3.1 (#247) @scala-steward
• Update discipline-scalatest to 2.1.0 (#246) @scala-steward
• Update scalatest to 3.2.3 (#245) @scala-steward
• Update scalacheck to 1.15.1 (#244) @scala-steward
• Update sbt-ci-release to 1.5.4 (#243) @scala-steward
• Update sbt to 1.4.2 (#242) @scala-steward
• Update scalacheck to 1.15.0 (#241) @scala-steward