chore: deploy a preview of PRs

Deploy PR previews to GitHub pages so changes can be viewed in a more
human-readable way.

NO-TICKET

.github/workflows/deploy-preview.yml

@@ -0,0 +1,40 @@
+name: Deploy PR Preview to GitHub Pages
+
+permissions:
+  contents: write
+  pull-requests: write
+
+on:
+  pull_request:
+    types:
+      - opened
+      - reopened
+      - synchronize
+      - closed
+
+concurrency: preview-${{ github.ref }}
+
+jobs:
+  deploy-preview:
+    name: Deploy PR preview to GitHub pages
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: npm
+
+      - name: Build
+        if: github.event.action != 'closed'
+        run: npm install && npm run build
+
+      - name: Deploy preview
+        uses: rossjrw/pr-preview-action@v1
+        with:
+          source-dir: ./dist/
+          token: ${{ secrets.GITHUB_TOKEN }}

README.md

@@ -5,14 +5,17 @@ This repository holds the OpenAPI documentation for the TIS Trainee API.
 
 The latest documentation is always available at [health-education-england.github.io/tis-trainee-api](https://health-education-england.github.io/tis-trainee-api/).
 
+Preview of open PRs are available by appending `/pr-preview/pr-{number}` to the end of the
+above path e.g. `health-education-england.github.io/tis-trainee-api/pr-preview/pr-123`.
+
 ## Developing
 
 ### Editing
 The [API documentation](openapi.yml) can be worked on within any text editor or
 IDE. Plugins are available for several popular IDEs.
 
 ### Previewing
-Several options are provided for previewing the documentation
+Several options are provided for previewing the documentation.
 
 #### Docker
 A [Docker compose](docker-compose.yml) file is provided for ease of use, the