Update node definitions

Author: Chuxel

containers/javascript-node-8-yarn/.devcontainer/Dockerfile

@@ -5,8 +5,13 @@
 
 FROM node:8-slim
 
-# Install git
-RUN apt-get update && apt-get -y install git
+# Install yarn and git
+RUN apt-get update \
+    && apt-get install -y apt-transport-https \
+    && curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add - \
+    && echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list \
+    && apt-get update \
+    && apt-get install -y yarn git
 
 # Install eslint
 RUN npm install -g eslint

containers/javascript-node-8-yarn/.devcontainer/devcontainer.json

@@ -1,5 +1,5 @@
 {
-	"name": "Node.js 8",
+	"name": "Node.js 8 & Yarn",
 	"dockerFile": ".devcontainer/Dockerfile",
 	"appPort": 3000,
 	"extensions": [