Select should start selecting values when closed and typing

### Issue type

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

* [ ] bug report
* [X] feature request

### Issue description

**Current behavior:**
One could argue this is a bug, but native select boxes work a lot better with the keyboard. Especially when it's time to select an item.

**Expected behavior:**
While the select box has focus, start typing should select the value that matches the keystroke.
Also, I should be able to type more than just the first letter. This becomes particularly annoying in selects that contain a list that we already know the answer, such as a country, a date, or month.

In a giant list of country, if you try to find "Canada", I should be able to type "can" and get right on it.
Same thing with months, or dates.

**The list should not have to be open for this to work.**

### Other information:

**npm, node, OS, Browser**
```
Windows
Chrome
```

**Angular, Nebular**
```
"@angular/common": "^8.2.14",
"@nebular/theme": "^4.6.0",
```