Add approach to override default names

via options:
```js
hljs.initLangOnLoad({
    overrideNames: {
		cs: "C-Sharp",
        csharp: "C-Sharp",
		fs: "F-Sharp",
	}
});
```

via HTML:
```html
<pre>
    <code data-lang-name="C-Sharp">
    ...
    </code>
</pre>
```
