Update Dockerfile for environment file handling

- Changed from moving to copying the .env.sample
- Updated path to use APACHE_DOCUMENT_ROOT for .env

Dockerfile

@@ -32,7 +32,7 @@ RUN set -eux; \
 
 USER www-data
 WORKDIR ${WEBSITE_ROOT}
-RUN mv .env.sample .env
+COPY .env.sample ${APACHE_DOCUMENT_ROOT}/.env
 RUN composer install
 RUN php bin/console asset-map:compile