fix: package action (#3)

Package action output per github docs.

package.json

@@ -2,8 +2,9 @@
     "name": "vault-action",
     "version": "0.1.0",
     "description": "A Github Action that allows you to consume vault secrets as secure environment variables.",
-    "main": "index.js",
+    "main": "dist/index.js",
     "scripts": {
+        "build": "ncc build index.js -o dist",
         "test": "jest",
         "test:integration": "jest -c integration/jest.config.js",
         "test:e2e": "jest -c e2e/jest.config.js"
@@ -41,6 +42,7 @@
     },
     "devDependencies": {
         "@types/jest": "^24.0.18",
+        "@zeit/ncc": "^0.20.5",
         "jest": "^24.9.0",
         "jest-when": "^2.7.0",
         "semantic-release": "^15.13.24"