a11y: Incorrect Usage of aria-expanded Attribute in ngx-bootstrap Typeahead Component

[haneefxello]

Bug description:
The typeahead component in ngx-bootstrap erroneously adds the aria-expanded attribute to the input field, causing an accessibility issue with the message "ARIA attribute is not allowed: aria-expanded="false". According to the accessibility guidelines outlined on Mozilla Developer Network, the aria-expanded attribute should only be associated with specific roles, such as buttons or combo lists.

This issue is observable in the example provided on the ngx-bootstrap website, particularly in the following link: https://valor-software.com/ngx-bootstrap/#/components/typeahead?tab=overview#Basic-array. Testing this example using axe devtools or Lighthouse reveals the presence of the accessibility issue.

Here is the ngx-bootstrap website link that reproduces the issue:
https://valor-software.com/ngx-bootstrap/#/components/typeahead?tab=overview#Basic-array

Here is the screenshot of the axe devtools accessibility report:

Versions of ngx-bootstrap, Angular, and Bootstrap:

ngx-bootstrap: 8.0.0

Angular: 13.3.10

Bootstrap: Not relevant

Build system: Angular CLI, System.js, webpack, starter seed:

Expected behavior
The typeahead input field in ngx-bootstrap should only utilize supported ARIA attributes in accordance with accessibility guidelines.