Should error if a tab is used outside of a tabs

[illicitonion]

This <tab> is not inside a <tabs> so it doesn't get displayed:

curriculum/common-content/en/module/js2/access/index.md

Lines 103 to 120 in 474ad5a

	{{<tab name="Predict and explain 💬 🧠">}}
	```js
	const profileData = {
	firstName: "Francesco",
	lastName: "Leoni",
	age: 33,
	};
	console.log(profileData.cityOfResidence);
	profileData.cityOfResidence = "Manchester";
	console.log(profileData.cityOfResidence);
	```
	Predict and explain what the console output will be when the code above runs.
	{{</tab>}}

We should make this a hard error. It doesn't make sense to create a <tab> which isn't part of a <tabs>.

(I will fix this one case, but we should prevent it in the future / detect other places someone may have accidentally done this)