Publish NPM package

Create NPM account and activate it

Open https://www.npmjs.com/ by browser, then click right-top [Sign up] button.
Fill Username, Email address and Password, then agree EULA and Privacy Policy and click [Create an account] button.
Open "[npm] Welcome..." mail by mailer, then click [Verify email address] button on the mail body.
- Without this verify step, npm publish will fail with 403 Forbidden error.
Reload https://www.npmjs.com/

Local NPM configuration

Run npm adduser, then input username, password and email address.
Check whether ~/.npmrc is created.
Check whether npm whoami returns NPM account name.

Prepare NPM contents

Check install and lint
```
npm install
npm run lint
```
Prepare package on ./npm folder
```
npm run prepare-npm
```

Publish NPM packag

Check what contents are published by dry-run.
```
npm publish ./npm --access=public --dry-run
```
Publish NPM package.
```
npm publish ./npm --access=public
```