add a shimmering loader

apple/OmnivoreKit/Sources/App/Views/Home/HomeFeedViewIOS.swift

@@ -155,6 +155,7 @@ private let enableGrid = UIDevice.isIPad || FeatureFlag.enableGridCardsOnPhone
             }
           }
         }
+        ShimmeringLoader()
         if prefersListLayout || !enableGrid {
           HomeFeedListView(prefersListLayout: $prefersListLayout, viewModel: viewModel)
         } else {

apple/OmnivoreKit/Sources/Views/ShimmerView.swift

@@ -0,0 +1,54 @@
+import SwiftUI
+
+public struct ShimmeringLoader: View {
+  @State private var phase: CGFloat = 0
+
+  public init() {}
+
+  public var body: some View {
+    ZStack {
+      Color.systemBackground
+      Color.appGraySolid
+        .contentShape(Rectangle())
+        .modifier(AnimatedMask(phase: phase).animation(
+          Animation.linear(duration: 2.0)
+            .repeatForever(autoreverses: false)
+        ))
+        .onAppear { phase = 0.8 }
+    }
+    .frame(height: 2)
+    .frame(maxWidth: .infinity)
+  }
+
+  /// An animatable modifier to interpolate between `phase` values.
+  struct AnimatedMask: AnimatableModifier {
+    var phase: CGFloat = 0
+
+    var animatableData: CGFloat {
+      get { phase }
+      set { phase = newValue }
+    }
+
+    func body(content: Content) -> some View {
+      content
+        .mask(GradientMask(phase: phase).scaleEffect(3))
+    }
+  }
+
+  /// An animatable gradient between transparent and opaque to use as mask.
+  /// The `phase` parameter shifts the gradient, moving the opaque band.
+  struct GradientMask: View {
+    let phase: CGFloat
+    let centerColor = Color.appGraySolid
+    let edgeColor = Color.clear
+
+    var body: some View {
+      LinearGradient(gradient:
+        Gradient(stops: [
+          .init(color: edgeColor, location: phase),
+          .init(color: centerColor, location: phase + 0.1),
+          .init(color: edgeColor, location: phase + 0.2)
+        ]), startPoint: .leading, endPoint: .trailing)
+    }
+  }
+}