2.1: Buttons Basic example
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**Primary Actor**: User

**Scope**: Ngx-bootstrap DEMO / BS version 3&4

**Goal**: Show user basic buttons example

Main success scenario:
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1. User opens Buttons demo page
2. User clicks on Basic sub-menu
3. User see 1 button with text: "Single Button"
4. Button should be clickable

Variations:
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2*. User scrolls to Basic sub-menu