Fix: Install required PHP extensions (exif, zip) for Laravel 7.x

The php:7.4-cli image is missing ext-exif and ext-zip which are required by:
- spatie/image (requires ext-exif)
- spatie/laravel-backup (requires ext-zip)
- spatie/laravel-medialibrary (depends on spatie/image)

Installing libzip-dev and using docker-php-ext-install to add these extensions.

.drone.yml

@@ -7,6 +7,8 @@ steps:
   - name: test
     image: php:7.4-cli
     commands:
+      - apt-get update && apt-get install -y libzip-dev
+      - docker-php-ext-install exif zip
       - curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer --version=2.2.24
       - composer install --prefer-dist --no-progress --no-interaction
       - composer validate --strict