Badge on Buttons

### Issue type

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

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

### Issue description
How do I get a badge on a button? I can see its working with tabs but it doesn't appear to work on the buttons
**Current behavior:**

**Expected behavior:**
Have a button with the same badge text as the tab in the tabs example
**Steps to reproduce:**

**Related code:**
```

{{ branch.name }}
```

### Other information:
Node v12.3.1
NPM 6.11.3
Windows 10
Chrome
**npm, node, OS, Browser**
```

```

**Angular, Nebular**
```
"@angular/animations": "~8.2.5",
"@angular/cdk": "^8.0.0",
"@angular/common": "~8.2.5",
"@angular/compiler": "~8.2.5",
"@angular/core": "~8.2.5",
"@angular/forms": "~8.2.5",
"@angular/platform-browser": "~8.2.5",
"@angular/platform-browser-dynamic": "~8.2.5",
"@angular/router": "~8.2.5",
"@nebular/auth": "^4.3.1",
"@nebular/eva-icons": "4.3.1",
"@nebular/security": "4.3.1",
"@nebular/theme": "^4.3.1",
```