feat: add deprecation alias for download command

We're removing the theme settings download command, but rather than
break people's setups, we will provide an alias and alert them that they
should change their tooling.

src/commands/theme/settings/download.ts

@@ -0,0 +1,15 @@
+import {renderWarning} from '@shopify/cli-kit/node/ui'
+import Pull from './pull.js'
+
+export default class Download extends Pull {
+  static hidden = true
+
+  async run() {
+    renderWarning({
+      headline: ['The', {command: 'shopkeeper theme settings download'}, 'command is deprecated.'],
+      body: ['Use', {command: 'shopify theme settings pull'}, 'instead.'],
+    })
+
+    await super.run()
+  }
+}