npm install typescript and create tsconfig file

Author: jordangarcia

packages/optimizely-sdk/package-lock.json

@@ -56,6 +56,7 @@
     "mocha-lcov-reporter": "^1.3.0",
     "nock": "^7.7.2",
     "sinon": "^2.3.1",
+    "typescript": "^3.3.3",
     "webpack": "^4.25.1",
     "webpack-cli": "^3.1.2"
   },

packages/optimizely-sdk/package.json

@@ -0,0 +1,8 @@
+{
+  "compilerOptions": {
+    "outDir": "./built",
+    "allowJs": true,
+    "target": "es5"
+  },
+  "include": ["./lib/**/*"]
+}