[ADD] News, Browse and Settings views ported to SwiftUI

This commit contains WIP SwiftUI versions of most of the views in SideStore.

AltStore/Views/Browse/AddSourceView.swift

@@ -0,0 +1,54 @@
+//
+//  AddSourceView.swift
+//  SideStore
+//
+//  Created by Fabian Thies on 20.11.22.
+//  Copyright © 2022 Fabian Thies. All rights reserved.
+//
+
+import SwiftUI
+
+struct AddSourceView: View {
+    
+    @State var sourceUrlText: String = ""
+    
+    var continueHandler: (_ urlText: String) -> ()
+    
+    var body: some View {
+        List {
+            Section {
+                TextField("https://connect.altstore.ml", text: $sourceUrlText)
+                    .keyboardType(.URL)
+                    .autocapitalization(.none)
+                    .autocorrectionDisabled()
+            } header: {
+                Text("Source URL")
+            } footer: {
+                VStack(alignment: .leading, spacing: 4) {
+                    Text("Please enter the source url here. Then, tap continue to validate and add the source in the next step.")
+                    
+                    HStack(alignment: .top) {
+                        Image(systemName: "exclamationmark.triangle.fill")
+                        
+                        Text("Be careful with unvalidated third-party sources! Make sure to only add sources that you trust.")
+                    }
+                }
+            }
+            
+            SwiftUI.Button {
+                self.continueHandler(self.sourceUrlText)
+            } label: {
+                Text("Continue")
+            }
+            .disabled(URL(string: self.sourceUrlText)?.host == nil)
+        }
+        .listStyle(InsetGroupedListStyle())
+        .navigationTitle("Add Source")
+    }
+}
+
+struct AddSourceView_Previews: PreviewProvider {
+    static var previews: some View {
+        AddSourceView(continueHandler: { _ in })
+    }
+}