Revert "Drop iOS 14 and macOS 11 support"

This reverts commit dcef7f47ff.

Vendor/RefreshControl/ScrollViewMatcher/FramePreferenceKey.swift

@@ -0,0 +1,18 @@
+//
+//  FramePreferenceKey.swift
+//  SwiftUI_Pull_to_Refresh
+//
+//  Created by Geri Borbás on 21/09/2021.
+//
+
+import Foundation
+import SwiftUI
+
+struct FramePreferenceKey: PreferenceKey {
+    typealias Value = CGRect
+    static var defaultValue = CGRect.zero
+
+    static func reduce(value: inout CGRect, nextValue: () -> CGRect) {
+        value = nextValue()
+    }
+}