Font files from third-party

### Issue type

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

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

### Issue description

**Current behavior:**
When you create the app in production mode, every font file from third-party are created in the root directory (/dist) instead the fonts folder. I do not found way to change this behavior. And this present a dirty document root

**Expected behavior:**
The posibility of indicate the folder to create the font files or a unique file with all fonts.

**Steps to reproduce:**
execute npm run:build prod with fonts from third-party.
### Other information:

**npm, node, OS, Browser**
```
# node -v
v8.11.3

#npm -v
6.4.1
```

**Angular, Nebular**
```
"@angular/core": "^7.0.3",
"@nebular/theme": "^3.4.1",
"roboto-fontface": "0.8.0",
```