SwiftNIO 2.4.0

SemVer Minor

• Add a WebSocket client upgrader. (#1038)
• EventLoopPromise.completeWith(Future), mirroring ELF.cascade(to:) (#1053)

SemVer Patch

• HTTPDecoder: Don't invoke left overs strategy on EOF (#1061)
• check breakages: fail loudly when unable to checkout tag (#1060)
• Check jq is available before checking API breakages (#1058)
• various patches (#1063, #1051, #1050)