Add support for scrolling the discovery tab to the top/first tab

Mastodon/Protocol/ScrollViewContainer.swift

@@ -14,6 +14,12 @@ protocol ScrollViewContainer: UIViewController {
 
 extension ScrollViewContainer {
     func scrollToTop(animated: Bool) {
-        scrollView.scrollRectToVisible(CGRect(origin: .zero, size: CGSize(width: 1, height: 1)), animated: animated)
+        scrollView.scrollToTop(animated: animated)
+    }
+}
+
+extension UIScrollView {
+    func scrollToTop(animated: Bool) {
+        scrollRectToVisible(CGRect(origin: .zero, size: CGSize(width: 1, height: 1)), animated: animated)
     }
 }

Mastodon/Scene/Discovery/DiscoveryViewController.swift

@@ -131,6 +131,13 @@ extension DiscoveryViewController: ScrollViewContainer {
     var scrollView: UIScrollView {
         return (currentViewController as? ScrollViewContainer)?.scrollView ?? UIScrollView()
     }
+    func scrollToTop(animated: Bool) {
+        if scrollView.contentOffset.y <= 0 {
+            scrollToPage(.first, animated: animated)
+        } else {
+            scrollView.scrollToTop(animated: animated)
+        }
+    }
 }
 
 extension DiscoveryViewController {

Mastodon/Scene/Search/Search/SearchViewController.swift

@@ -190,6 +190,16 @@ extension SearchViewController: UISearchControllerDelegate {
     }
 }
 
+// MARK: - ScrollViewContainer
+extension SearchViewController: ScrollViewContainer {
+    var scrollView: UIScrollView {
+        discoveryViewController?.scrollView ?? UIScrollView()
+    }
+    func scrollToTop(animated: Bool) {
+        discoveryViewController?.scrollToTop(animated: animated)
+    }
+}
+
 // MARK: - UICollectionViewDelegate
 //extension SearchViewController: UICollectionViewDelegate {
 //    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {