Re-add a test workflow for pull requests

.github/workflows/build_deploy.yaml

@@ -0,0 +1,38 @@
+---
+name: Build and Deploy
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  build_and_deploy:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: cachix/install-nix-action@v26
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+
+      - uses: actions/checkout@v4
+
+      - name: Install dependencies
+        run: ./run ci:install
+
+      - name: Run tests
+        run: ./run ci:test
+
+      - name: Generate the website
+        run: |
+          ./run ci:build
+          tree output_prod
+
+      - name: Install the deploy key and known hosts
+        run: |
+          mkdir -p ~/.ssh && chmod 700 ~/.ssh
+          echo "${{ secrets.SSH_DEPLOY_KEY }}" > ~/.ssh/deploy && chmod 600 ~/.ssh/deploy
+          echo "${{ secrets.SSH_KNOWN_HOSTS }}" > ~/.ssh/known_hosts && chmod 600 ~/.ssh/known_hosts
+
+      - name: Deploy the website
+        run: ssh -i ~/.ssh/deploy oliverdavies-uk@ssh.oliverdavies.uk