chore: setup pkg.pr.new (#12977)

Author: benmccann

.github/workflows/ci.yml

@@ -19,14 +19,25 @@ permissions:
   contents: read # to fetch code (actions/checkout)
 
 jobs:
+  pkg-pr-new:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: pnpm/action-setup@v4.0.0
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: pnpm
+      - run: pnpm install --frozen-lockfile
+      - run: pnpx pkg-pr-new publish --comment=off ./packages/kit
   lint-all:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
       - uses: pnpm/action-setup@v4.0.0
       - uses: actions/setup-node@v4
         with:
-          node-version: '18.x'
+          node-version: 22
           cache: pnpm
       - run: pnpm install --frozen-lockfile
       - run: pnpm run lint

CONTRIBUTING.md

@@ -22,7 +22,7 @@ pnpm install
 
 You can use the playground at [`playgrounds/basic`](./playgrounds/basic/) to experiment with your changes to SvelteKit locally.
 
-### Linking
+### Linking local changes
 
 If you want to test against an existing project, you can use [pnpm `overrides`](https://pnpm.io/package_json#pnpmoverrides) in that project:
 
@@ -39,6 +39,14 @@ If you want to test against an existing project, you can use [pnpm `overrides`](
 }
 ```
 
+### Testing PR changes
+
+Each pull request will be built and published via [pkg.pr.new/](https://pkg.pr.new/). You can test the change by installing the package with your PR number:
+
+```
+npm add https://pkg.pr.new/sveltejs/kit/@sveltejs/kit@YOUR_PR_NUMBER_GOES_HERE
+```
+
 ## Code structure
 
 Entry points to be aware of are: