Vapor 4 leaf - failed to resolve dependency

After creating a new vapor project vapor new someProjectName using terminal while also adding fluent and postgres as my DB... everything goes well, however, after adding leaf manually I get a failed to resolve dependency error, this is what I have on my Package.swift file:

// swift-tools-version:5.2
import PackageDescription

let package = Package(
    name: "someProjectName",
    platforms: [
       .macOS(.v10_15)
    ],
    dependencies: [
        // 💧 A server-side Swift web framework.
        .package(url: "https://github.com/vapor/vapor.git", from: "4.0.0"),
        .package(url: "https://github.com/vapor/fluent.git", from: "4.0.0"),
        .package(url: "https://github.com/vapor/fluent-postgres-driver.git", from: "2.0.0"),
        .package(url: "https://github.com/vapor/leaf.git", from: "3.0.0"),
    ],
    targets: [
        .target(
            name: "App",
            dependencies: [
                .product(name: "Fluent", package: "fluent"),
                .product(name: "FluentPostgresDriver", package: "fluent-postgres-driver"),
                .product(name: "Vapor", package: "vapor"),
                .product(name: "Leaf", package: "leaf")
            ],
            swiftSettings: [
                // Enable better optimizations when building in Release configuration. Despite the use of
                // the `.unsafeFlags` construct required by SwiftPM, this flag is recommended for Release
                // builds. See <https://github.com/swift-server/guides#building-for-production> for details.
                .unsafeFlags(["-cross-module-optimization"], .when(configuration: .release))
            ]
        ),
        .target(name: "Run", dependencies: [.target(name: "App")]),
        .testTarget(name: "AppTests", dependencies: [
            .target(name: "App"),
            .product(name: "XCTVapor", package: "vapor"),
        ])
    ]
)

it must be that I am adding the leaf dependency wrong, and after reviewing vapor's documentation they haven't updated their docs either... please let me know if you know the answer to this. thanks!

Leaf is still in RC which is why you can't find anything about it unfortunately.

Set the version to 4.0.0-rc and it should work