Add a separate 5.7 Package.swift to please Xcode

Doesn't work w/ 5.7.

Author: helje5

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.7
+// swift-tools-version:5.6
 
 import PackageDescription
 

Package@swift-5.7.swift

@@ -0,0 +1,26 @@
+// swift-tools-version:5.7
+
+import PackageDescription
+
+var package = Package(
+  name: "Northwind",
+
+  platforms: [ .macOS(.v10_15), .iOS(.v13) ],
+  products: [
+    .library(name: "Northwind", targets: [ "Northwind" ])
+  ],
+  
+  dependencies: [
+    .package(url: "git@github.com:55DB091A-8471-447B-8F50-5DFF4C1B14AC/Lighter.git",
+             branch: "develop"),
+    .package(url: "https://github.com/apple/swift-docc-plugin", from: "1.0.0")
+  ],
+  
+  targets: [
+    .target(name         : "Northwind",
+            dependencies : [ "Lighter" ],
+            path         : "dist",
+            resources    : [ .copy("northwind.db") ],
+            plugins      : [ .plugin(name: "Enlighter", package: "Lighter") ])
+  ]
+)