Add unstable_tailwind and unstable_postcss to changesets

.changeset/famous-candles-begin.md

@@ -0,0 +1,37 @@
+---
+'@shopify/hydrogen': patch
+---
+
+Adopt Remix [`unstable_tailwind`](https://remix.run/docs/en/1.15.0/guides/styling#built-in-tailwind-support) and [`unstable_postcss`](https://remix.run/docs/en/1.15.0/guides/styling#built-in-postcss-support) future flags for the Demo Store template.
+
+### `unstable_tailwind` and `unstable_postcss` migration steps
+
+1. Move the file `<root>/styles/app.css` to `<root>/app/styles/app.css`, and remove it from `.gitignore`.
+
+2. Add `"browserslist": ["defaults"]` to your `package.json`, or your preferred [value from Browserslist](https://browsersl.ist/).
+
+3. Replace the `build` and `dev` scripts in your `package.json` with the following:
+
+   **Before**
+
+   ```json
+    "scripts": {
+      "build": "npm run build:css && shopify hydrogen build",
+      "build:css": "postcss styles --base styles --dir app/styles --env production",
+      "dev": "npm run build:css && concurrently -g --kill-others-on-fail -r npm:dev:css \"shopify hydrogen dev\"",
+      "dev:css": "postcss styles --base styles --dir app/styles -w",
+      ...
+    }
+   ```
+
+   **After**
+
+   ```json
+    "scripts": {
+      "dev": "shopify hydrogen dev",
+      "build": "shopify hydrogen build",
+      ...
+    }
+   ```
+
+You can also remove dependencies like `concurrently` if you don't use them anywhere else.

.changeset/tidy-papayas-check.md

@@ -1,5 +1,5 @@
 ---
-'@shopify/cli-hydrogen': patch
+'@shopify/hydrogen': patch
 ---
 
 Adopt Remix [`v2_errorBoundary`](https://remix.run/docs/en/release-next/route/error-boundary-v2) future flag