Add publish github action

.github/workflows/publish.yml

@@ -0,0 +1,17 @@
+name: Node.js Package Publish
+on:
+  release:
+    types: [created]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v2
+        with:
+          node-version: '12.x'
+          registry-url: 'https://registry.npmjs.org'
+      - run: npm ci
+      - run: npm publish --access public
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}

README.md

@@ -0,0 +1,10 @@
+# Pyth SDK JS
+The Pyth JavaScript SDK provides definitions and utilities for Pyth data structures. 
+
+Please see the [pyth.network documentation](https://docs.pyth.network/) for more information on how to use Pyth prices in various blockchains.
+
+## Releases
+
+We use [Semantic Versioning](https://semver.org/) for our releases. In order to release a new version of this package and publish it to npm, follow these steps: 
+1. Run `npm version <new version number> --no-git-tag-version`. This command will update the version of the package. Then push your changes to github.
+2. Once your change is merged into `main`, create a release with tag `v<new version number>` like `v1.5.2`, and a github action will automatically publish the new version of this package to npm.

package.json

@@ -18,8 +18,7 @@
     "prepare": "npm run build",
     "prepublishOnly": "npm test && npm run lint",
     "preversion": "npm run lint",
-    "version": "npm run format && git add -A src",
-    "postversion": "git push && git push --tags"
+    "version": "npm run format && git add -A src"
   },
   "keywords": [
     "pyth",