Add PHP syntax check, and (commented-out) custom block build

Closes #9

.drone.yml

@@ -2,6 +2,19 @@
 kind: pipeline
 name: deploy main branch to live site
 steps:
+  - name: php syntax check
+    image: php:8.3.7-cli
+    commands:
+      - for f in $(find /drone -name '*.php'); do php -l "$f"; done
+  # If a custom block is in use, uncomment this (and make sure package.json
+  # includes `scripts.build`, and change the `depends_on` below 
+  # - name: compile custom block
+  #   image: node:18.18.2
+  #   commands:
+  #     - npm install
+  #     - npm run build
+  #   depends_on:
+  #     - php syntax check
   - name: docker cp deploy
     image: git.coopcloud.tech/coop-cloud/docker-cp-deploy:latest
     settings:
@@ -13,6 +26,8 @@ steps:
       dest: /var/www/html/
       deploy_key:
         from_secret: drone_ssh_server.example.com
+    depends_on:
+      - php syntax check
     when:
       branch:
        - main