implemented option to add bcmath to laradock php-worker (#1716)

* implemented option to add bcmath to laradock php-worker
* updated docs

php-worker/Dockerfile

@@ -25,6 +25,12 @@ RUN apk --update add wget \
 RUN docker-php-ext-install mysqli mbstring pdo pdo_mysql tokenizer xml pcntl
 RUN pecl channel-update pecl.php.net && pecl install memcached mcrypt-1.0.1 && docker-php-ext-enable memcached
 
+#Install BCMath package:
+ARG INSTALL_BCMATH=false
+RUN if [ ${INSTALL_BCMATH} = true ]; then \
+    docker-php-ext-install bcmath \
+;fi
+
 # Install PostgreSQL drivers:
 ARG INSTALL_PGSQL=false
 RUN if [ ${INSTALL_PGSQL} = true ]; then \