Update the install script

Write an install script 
```
"scripts": {
   "build": "./build.sh"
},
```
that 
1. Creates the `data/` directory
2. Installs the rsl script
3. Runs `npm install` to install dependencies

Also set minimum version of node. I tested on `v18.17.0`
```
  "engines": {
    "node": ">=18.17.0"
  },
```