Bump minimum deployment target to match swift-syntax

Author: kateinoigakukun

Package.swift

@@ -10,6 +10,13 @@ let useLegacyResourceBundling =
 
 let package = Package(
     name: "JavaScriptKit",
+    platforms: [
+        .macOS(.v10_15),
+        .iOS(.v13),
+        .tvOS(.v13),
+        .watchOS(.v6),
+        .macCatalyst(.v13),
+    ],
     products: [
         .library(name: "JavaScriptKit", targets: ["JavaScriptKit"]),
         .library(name: "JavaScriptEventLoop", targets: ["JavaScriptEventLoop"]),