Documentation: add Node Pebble installation instructions to Install section

[aral]

I just created a Node module called Node Pebble that makes it trivial to launch and use Pebble in unit tests from Node.js:

https://www.npmjs.com/package/@small-tech/node-pebble

It could help client developers working with Node.js if is mentioned in the Install and Usage sections. e.g.,

## Install

### Binary
… (see #308)
### Go
…
### Node.js
`​``sh
npm install @small-tech/node-pebble
`​``

## Usage
…
### Node.js
`​``js
const Pebble = require('node-pebble')

(async () => {
  await Pebble.ready()
  // Run your tests…
  await Pebble.shutdown()
}()
`​``

Note that as of the latest version of Node Pebble, the module automatically handles patching Node.js’s TLS module to accept the Pebble test cert as well as the dynamically-generated Pebble root and intermediary CA certificates so when await Pebble.ready() returns, Node.js is ready accept responses from Pebble without any further work on the part of the developer.

Happy to prepare a pull request for this if you feel it’s worthwhile to include it.

Related #308, #309

[jsha]

Thanks so much for letting us know! Since this is specific to one language environment I don't think it makes sense to add to our overall README, but hopefully other folks who are doing Node integrations will find this issue and through it, your module.

[aral]

Sure, closing :)