Impossible to nest angular components into nebular

### Issue type

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

* [x] bug report
* [ ] feature request

### Issue description

**Current behavior:**
Nesting angular component into tag is just impossible. The component is not rendenred and his contents is not displayed on the page. Actually it is the same problem like described here: https://stackoverflow.com/questions/61311022/how-do-i-nest-components-using-the-nebular-ui-kit
I see nobody helped this gut but he is absolutely right, the problem exists!

**Expected behavior:**
Contents of nested component should appear on the page.

**Steps to reproduce:**
I generated two components in my angular app. First one contain tag and inside of this tag I added another component which has only .

**Related code:**
```
first.component.html
Whatever

second.component.html

```

### Other information:

**npm, node, OS, Browser**
```
Node, npm: `node --version` => v14.16.0
`npm --version` => 6.14.11
OS: Windows (7/8/10).
Browser: Chrome
```

**Angular, Nebular**
```
Nebular 7.0.0
Angular 12.0.0
```