fix(cli): adapt Package.swift to work on older Swift versions (#10687)

I noticed the plugin build fails on older Swift (tested on macOS 12) because the default minimum required macOS version (10.10 in my case) is older than `v10_13` which is set by the Tauri iOS package (and also swift-rs).
So the plugins must explicitly define a minimum macOS version too.

.changes/fix-ios-build-older-swift.md

@@ -0,0 +1,6 @@
+---
+'tauri-cli': 'patch:bug'
+'@tauri-apps/cli': 'patch:bug'
+---
+
+Fix Swift plugin compilation on older versions.

examples/api/src-tauri/tauri-plugin-sample/ios/Package.swift

@@ -8,6 +8,7 @@ import PackageDescription
 let package = Package(
     name: "tauri-plugin-sample",
     platforms: [
+        .macOS(.v10_13),
         .iOS(.v13),
     ],
     products: [

tooling/cli/templates/plugin/ios-spm/Package.swift

@@ -6,6 +6,7 @@ import PackageDescription
 let package = Package(
     name: "tauri-plugin-{{ plugin_name }}",
     platforms: [
+        .macOS(.v10_13),
         .iOS(.v13),
     ],
     products: [