[ADD] Backported dismiss() environment variable to let views dismiss themselves

AltStore/Views/Browse/ConfirmAddSourceView.swift

@@ -65,18 +65,8 @@ struct ConfirmAddSourceView: View {
                 confirmationHandler(fetchedSource)
             } label: {
                 Label(title: { Text("Add Source") }, icon: { Image(systemName: "plus") })
-                    .multilineTextAlignment(.center)
-                    .foregroundColor(.white)
-                    .padding()
-                    .frame(
-                        maxWidth: .infinity,
-                        alignment: .bottomLeading
-                    )
-                    .background(
-                        RoundedRectangle(cornerRadius: 10)
-                            .foregroundColor(Color.accentColor)
-                    )
             }
+            .buttonStyle(FilledButtonStyle())
             .padding()
         }
         .background(Color(UIColor.systemGroupedBackground).ignoresSafeArea())

AltStore/Views/Browse/SourcesView.swift

@@ -12,6 +12,9 @@ import CoreData
 
 struct SourcesView: View {
     
+    @Environment(\.dismiss)
+    private var dismiss
+    
     @Environment(\.managedObjectContext)
     var managedObjectContext
     
@@ -102,9 +105,7 @@ struct SourcesView: View {
             }
             
             ToolbarItem(placement: .navigationBarTrailing) {
-                SwiftUI.Button {
-                    self.isShowingAddSourceAlert = false
-                } label: {
+                SwiftUI.Button(action: self.dismiss) {
                     Text("Done").bold()
                 }
             }