Webpack 4 with ngx-admin

### Issue type

**I'm submitting a ...** (check one with "x")

* [ X ] bug report
* [ ] feature request
* [ ] question about the decisions made in the repository

### Issue description

**Current behavior:**
I am trying to work with webpack 4 with ngx-admin project- But all the theme style is not working. Everything compiled successfully and the angular is running, except the theme style.
I am probably missing something but I am not sure what.

**Expected behavior:**
To be able to run the ngx-admin with webpack 4.

**Steps to reproduce:**
1. I cloned the ngx-admin start kit
2. Added webpack configuration

**Related code:**

```
insert short code snippets here
```

### Other information:

**npm, node, OS, Browser**
```

```

**Angular, Nebular**
```

```