chore: set minimum Swift version to 6.0 and remove platform constraints

- Update swift-tools-version from 5.9 to 6.0
- Remove explicit platform constraints (pure Swift types work on all platforms)
- Remove unused Foundation import from Input.Type.swift

Align with Swift Testing framework requirement and CI coverage (Swift 6.0 and 6.2).

Author: coenttb

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.9
+// swift-tools-version:6.0
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription
@@ -23,13 +23,6 @@ extension Target.Dependency {
 
 let package = Package(
     name: "swift-html-types",
-    platforms: [
-        .macOS(.v13),
-        .iOS(.v16),
-        .tvOS(.v16),
-        .watchOS(.v9),
-        .visionOS(.v1)
-    ],
     products: [
         .library(name: .htmlTypes, targets: [.htmlTypes]),
         .library(name: .htmlTypesFoundation, targets: [.htmlTypesFoundation]),

Sources/HTMLTypes/Conveniences/Input.Type.swift

@@ -5,7 +5,6 @@
 //  Created by Coen ten Thije Boonkkamp on 11/07/2025.
 //
 
-import Foundation
 import HTMLAttributeTypes
 
 extension Input.Variant {