Add an ngrok service for sharing the local environment

We have a working proof of concept courtesy of @kadamwhite so far:

Instructions:

- Create the current two files in a new directory.
- run `npm install`
- run `TARGET_HOST=dev.altis.dev npm start` while replacing `dev.altis.dev` with your local env domain
- Figure out your machine network local IP
- View the site at http://LOCAL-IP-HERE:3000

## server.js:

```js
const express = require( 'express' );
const morgan = require( 'morgan' );
const proxy = require( 'http-proxy-middleware' );
const ngrok = require( 'ngrok' );

const createProxyMiddleware = proxy.createProxyMiddleware;
const responseInterceptor = proxy.responseInterceptor;

const PORT = 3000;
const HOST = 'localhost';
const TARGET_HOST = process.env.TARGET_HOST;

( async () => {
const externalUrl = await ngrok.connect( PORT );

const externalHost = externalUrl.replace( /https?:\/\//, '' );

const app = express();

app.use( morgan( 'dev' ) );

// Proxy everything.
app.use( '/', createProxyMiddleware( {
target: TARGET_HOST,

changeOrigin: true,

// Defer res.end() to be handled by responseInterceptor.
selfHandleResponse: true,

/**
* Intercept response and replace Snopes URL with ngrok URL.
* Remove integrity hashes from markup so static assets load.
**/
onProxyRes: responseInterceptor( async ( responseBuffer ) => {
return responseBuffer.toString( 'utf8' )
// Point Tachyon URLs at a web-accessible bucket.
.replace( /TARGET_HOST\/tachyon/ig, 'LIVE_HOST/tachyon' )
// Everything else, rewrite so it will load that resource
// over the ngrok connection.
.replace( /TARGET_HOST/ig, externalHost )
// Remove integrity hashes entirely :( or things won't work.
.replace( /integrity=('[^']+'|"[^"]+")/ig, '' );
} ),
} ) );

app.listen( PORT, HOST, () => {
console.log( `Starting local Proxy at ${HOST}:${PORT}` );
console.log( `Local environment is now available at ${ externalUrl }` );
} );

} )();
```

## package.json:

```json
{
"name": "local-server-proxy",
"private": true,
"version": "1.0.0",
"description": "Relay web traffic from an external URL to Local Server",
"main": "index.js",
"scripts": {
"proxy": "node server.js",
"start": "node server.js"
},
"author": "Human Made",
"license": "MIT",
"dependencies": {
"express": "^4.17.1",
"http-proxy-middleware": "^2.0.1",
"morgan": "^1.10.0",
"ngrok": "^4.1.0"
}
}
```

Acceptance criteria:

- [ ] Create a containerised version of the above node app
- [ ] Add a command called `composer server share` that starts the service
- [ ] A SIGQUIT input should stop the service eg. ctrl+c

Start with the supplied server.js and package.json proof of concept, then inspect the repository's existing Composer command conventions. Containerize the Node app, add the `composer server share` command, and verify that Ctrl+C sends SIGQUIT and stops the service.

Written by the indexing model from the issue text.