Close nb popover when user scrolls screen

### Issue type

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

* [ ] bug report
* [x] feature request

### Issue description

**Current behavior:**
Currently, there are scroll strategies available in cdk/overlay and they are being used with NbSelectComponent. Is there any way to get these with the nbpopover?

**Expected behavior:**
The nbpopover can be closed when user scrolls to screen, allowing the user to view the page completely.

### Other information:

**npm, node, OS, Browser**
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