fix: add direct swift-rfc-5322 dependency to force version 0.4.0

Work around CI cache issues by explicitly depending on swift-rfc-5322 0.4.0.

Author: coenttb

Package.swift

@@ -20,7 +20,8 @@ let package = Package(
         .package(url: "https://github.com/swift-standards/swift-ieee-754", from: "0.1.0"),
         .package(url: "https://github.com/swift-standards/swift-rfc-2045", from: "0.1.0"),
         .package(url: "https://github.com/swift-standards/swift-rfc-2046", from: "0.1.0"),
-        .package(url: "https://github.com/swift-standards/swift-rfc-2183", from: "0.3.0")
+        .package(url: "https://github.com/swift-standards/swift-rfc-2183", from: "0.3.0"),
+        .package(url: "https://github.com/swift-standards/swift-rfc-5322", from: "0.4.0"),
     ],
     targets: [
         .target(