title: Allow check only one checkbox and get value of checked
body: <p>I got at this moment only 2 checkboxes, what I want to achieve?
  If you check checkbox for example - value 2 ( but you previously checked value 1 ) I want to uncheck value1 and select only value2. And if you want to select again value1 then uncheck value2.</p>
  <p>I prepared stackblitz for my issue
  <a href="https://stackblitz.com/edit/angular-pr9rf3?file=src/app/app.component.ts" rel="nofollow noreferrer">https://stackblitz.com/edit/angular-pr9rf3?file=src/app/app.component.ts</a></p>
  <p>I want to allow select only one checkbox then disable second but I want also to uncheck this so I can again select checkbox.</p>