Revert "Drop iOS 14 and macOS 11 support"

This reverts commit dcef7f47ff.

Backports/Tint+Backport.swift

@@ -0,0 +1,11 @@
+import SwiftUI
+
+extension Backport where Content: View {
+    @ViewBuilder func tint(_ color: Color?) -> some View {
+        if #available(iOS 15.0, macOS 12.0, tvOS 15.0, *) {
+            content.tint(color)
+        } else {
+            content.foregroundColor(color)
+        }
+    }
+}