Added Travis build for the VSCode extension

Author: fwcd

.travis.yml

@@ -1,3 +1,10 @@
-language: java
-install: ./gradlew install
-script: ./gradlew build -i
+matrix:
+  include:
+    - language: java
+      install: ./gradlew install
+      script: ./gradlew build -i
+    
+    - language: node_js
+      install:
+        - npm install
+        - npm run compile