Issue title: How to import all languages 
 Issue body: Hi, I want to import all languages in one place and have the ability to automatically detect the language.
 Comments: 
 Comment 0: Closing as does not follow the issue template
 Comment 1:  > I want to import all languages in one place

You still have to import the languages individually as mentioned in the docs.

> have the ability to automatically detect the language

it already detects the language for you
 Comment 2: For me, `import` doesn't work, but with `require` it's ok: 

```typescript
export function hljsLanguages() {
    return [
        { name: 'typescript', func: require('highlight.js/lib/languages/typescript') },
        { name: 'javascript', func: require('highlight.js/lib/languages/javascript') },
        { name: 'scss', func: require('highlight.js/lib/languages/scss') },
        { name: 'xml', func: require('highlight.js/lib/languages/xml') }
    ];
}
```
{'source': 'GithubIssues', 'repo_name_with_owner': 'MurhafSousli/ngx-highlightjs', 'issue_id': 391026175, 'repo_stars': 243.0}