Add typescript and fried-twinkie to be installed for PolyGerrit tests

A new test target is getting added to check for template type safety
and relies on these two packages.

Change-Id: I8cb74dd45139193a6be5f361653594b2c4c92b94
diff --git a/jenkins-docker/slave/Dockerfile b/jenkins-docker/slave/Dockerfile
index 6abb06d..9147a0a 100644
--- a/jenkins-docker/slave/Dockerfile
+++ b/jenkins-docker/slave/Dockerfile
@@ -56,7 +56,7 @@
 
 # PolyGerrit tests
 
-RUN npm install -g web-component-tester eslint eslint-config-google eslint-plugin-html polylint polymer-cli
+RUN npm install -g web-component-tester eslint eslint-config-google eslint-plugin-html polylint polymer-cli typescript fried-twinkie
 RUN curl -sL https://dl-ssl.google.com/linux/linux_signing_key.pub | apt-key add -
 RUN sh -c 'echo "deb http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google.list'
 RUN apt-get update && apt-get install -y google-chrome-stable