Rebrand Nostore to Nostash and set minimum deployment to iOS 18.0

Shared (App)/NostashApp.swift

@@ -0,0 +1,20 @@
+//
+//  NostashApp.swift
+//  Nostash
+//
+//  Created by Ryan Breen on 2/17/23.
+//
+
+import SwiftUI
+
+@main
+struct NostashApp: App {
+    var body: some Scene {
+        WindowGroup("Nostash") {
+            MainView()
+        }
+        #if macOS
+        .defaultSize(width: 400, height: 500)
+        #endif
+    }
+}