Install Prestissimo in Workspace

**Why we need this change?**

[Prestissimo](https://github.com/hirak/prestissimo) will enabled `composer` to install plugins in parallel.

**Source**

http://jackmcdade.com/blog/tired-of-waiting

workspace/Dockerfile-71

@@ -467,6 +467,19 @@ RUN if [ ${INSTALL_DEPLOYER} = true ]; then \
     composer global require "deployer/deployer" \
 ;fi
 
+#####################################
+# Prestissimo:
+#####################################
+USER laradock
+
+ARG INSTALL_PRESTISSIMO=false
+ENV INSTALL_PRESTISSIMO ${INSTALL_PRESTISSIMO}
+
+RUN if [ ${INSTALL_PRESTISSIMO} = true ]; then \
+    # Install Prestissimo
+    composer global require "hirak/prestissimo" \
+;fi
+
 #####################################
 # Linuxbrew:
 #####################################