2.4: Buttons Checkbox with Reactive Forms example
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**Primary Actor**: User

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

**Goal**: Show user checkbox-like buttons example with Reactive Forms

Main success scenario:
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1. User opens Buttons demo page
2. User clicks on Checkbox with Reactive Forms sub-menu
3. User see button-group, contain of 3 parts(labels), with the checkbox value field above it
4. By default, 1st button is inactive, 2d - active and 3d - inactive, and the text: "{"left": false, "middle": true, "right": false}" displayed in the button-checkbox value field above it.
5. User able to click on each button
6. When user clicks on the inactive button, it becomes active and the text in the checkbox value field next to this button name changed to "true"
7. User can make all buttons inactive and can make all buttons active
8. Component src should be written with usage of FormBuilder and FormGroup

Variations:
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2*. User scrolls to Checkbox with Reactive Forms sub-menu