feat(env): MW_BRANCH environment variable

Author: SomeMWDev

config/.env.example

@@ -14,6 +14,7 @@ MW_DOCKER_GID=1000
 COMPOSER_CACHE_DIR=/var/www/html/w/cache/composer
 MW_LOG_DIR=/var/www/html/w/cache
 MW_INSTALL_PATH=/var/www/html/w
+MW_BRANCH=master
 
 # Use idekey=VSCODE for VS Code
 # If you are using Docker Desktop on Windows/Mac or docker >= 20 on linux, set client_host=host.docker.internal