Add pull to refresh for Subscriptions, Popular and Trending (fixes #31)

Vendor/RefreshControl/README

@@ -0,0 +1,47 @@
+https://github.com/Geri-Borbas/iOS.Blog.SwiftUI_Pull_to_Refresh
+
+# SwiftUI Pull to Refresh
+⇣ SwiftUI Pull to Refresh (for iOS 13 and iOS 14) condensed into a single modifier.
+
+
+Complementary repository for article [**SwiftUI Pull to Refresh**] (in progress). See [`ContentView.swift`] for usage, and [`RefreshControlModifier.swift`] for the source. Designed to work with **multiple scroll views** on the same screen.
+
+```Swift
+struct ContentView: View {
+
+    var body: some View {
+        VStack {
+            HStack {
+                List {
+                    ForEach(1...100, id: \.self) { eachRowIndex in
+                        Text("Left \(eachRowIndex)")
+                    }
+                }
+                .refreshControl { refreshControl in
+                    Network.refresh {
+                        refreshControl.endRefreshing()
+                    }
+                }
+                List {
+                    ForEach(1...100, id: \.self) { eachRowIndex in
+                        Text("Right \(eachRowIndex)")
+                    }
+                }
+                .refreshControl { refreshControl in
+                    Network.refresh {
+                        refreshControl.endRefreshing()
+                    }
+                }
+            }
+        }
+    }
+}
+```
+
+
+## License
+
+> Licensed under the [**MIT License**](https://en.wikipedia.org/wiki/MIT_License).
+
+[`ContentView.swift`]: SwiftUI_Pull_to_Refresh/Views/ContentView.swift
+[`RefreshControl.swift`]: SwiftUI_Pull_to_Refresh/Views/RefreshControl.swift