Vue subscriptions example

```js
apollo: {
$subscribe: {
tagAdded: {
query: gqlsubscription test{listen(topic: "hello"){relatedNodeId}},
// Reactive variables
variables () {
// This works just like regular queries
// and will re-subscribe with the right variables
// each time the values change
return {
type: this.type,
}
},
// Result hook
result (data) {
console.log(data)
},
},
},
```

https://discordapp.com/channels/489127045289476126/498852330754801666/560214820121739285

Start by reviewing the Vue subscription snippet in the issue and the linked Discord discussion for the intended website location and context. Done means the website includes a clear Vue subscriptions example matching the requested usage and the example is checked for correctness.

Vom Indexierungsmodell aus dem Issue-Text verfasst.