Make nb-select work properly with autocomplete from HTML

[jsgoupil]

Issue type

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

• [ ] bug report
• [X] feature request

Issue description

Current behavior: nb-select does not handle the autocomplete functionality from HTML.

Expected behavior: This would be useful in a HTML such as a country selection, state selection etc.

Steps to reproduce:

        <nb-select [(ngModel)]="value.country" autocomplete="country">
            <nb-option value="">Select</nb-option>
            <nb-option value="CA">Canada</nb-option>
            <nb-option value="US">United States</nb-option>
        </nb-select>

Other information:

npm, node, OS, Browser

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Node, npm: `node --version` and `npm --version`
OS: Windows (7/8/10). Linux (incl. distribution). macOS (El Capitan? Sierra?)
Browser: Chrome/Safari/Firefox/etc?
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Angular, Nebular

Angular: 9.1.0
Nebular: 5.0.0

[jdgabriel]

Any solutions?