Element 'button' is not supported (for information on implementing this, see the support forums

Hi,

I am getting this error while adding button tag in html code. - "Element 'button' is not supported (for information on implementing this, see the support forums"

I want to add button tag like this.
<button type="button" onclick="alert('Hello world!')">Click Me!</button>

Here is my config.

'HTML_Allowed' => 'div,b,strong,i,em,a[href|title],ul,ol,li,p[style],br,span[style],img[width|height|alt|src],iframe[src|width|height|class|frameborder],blockquote, *[style|class],button[type]',
'CSS_AllowedProperties' => 'font,
font-size,
font-weight,
font-style,
font-family,
text-decoration,
padding-left,
color,
background-color,
text-align
',
'URI_SafeIframeRegexp' => '%^(https?:)?//(www.linkedin.com/embed/|www.youtube.com/embed/|player.vimeo.com/video/)%'

Start by reviewing how the HTML_Allowed configuration handles the unsupported button element and compare it with the supplied button example. Determine the intended sanitized output and security implications, then verify behavior with the project's existing validation tests; the issue names no files or tests, so the relevant entry point must first be located.