Add ability to install MSSQL drivers in php-worker

.env.example

@@ -293,6 +293,7 @@ PHP_WORKER_INSTALL_BCMATH=false
 PHP_WORKER_INSTALL_MEMCACHED=false
 # PHP_WORKER_INSTALL_OCI8 Does not work in php5.6 version
 PHP_WORKER_INSTALL_OCI8=false
+PHP_WORKER_INSTALL_MSSQL=false
 PHP_WORKER_INSTALL_PHALCON=false
 PHP_WORKER_INSTALL_SOAP=false
 PHP_WORKER_INSTALL_ZIP_ARCHIVE=false