download kml file throuth tag <a>,browser not handle mimeType 'application/vnd.google-earth.kml+xml'

when i use a tag for downloading kml file, browser doesn't recognize right extension.
then i try mimetype https://www.iana.org/assignments/media-types/media-types.xhtml, some works some doesn't.i use Chrome for the test.
any one can help? thanks...

let url = URL.createObjectURL(
         new Blob([string format kml data], { type: 'application/vnd.google-earth.kml+xml' })
       )
const link = document.createElement('a')
link.style.display = 'none'
link.href = url
link.setAttribute('download', 'filename')
document.body.appendChild(link)
link.click()
document.body.removeChild(link)
URL.revokeObjectURL(url)