luci-base: ui.js: set autocomplete="new-password" for password fields

Attempt to prevent Firefox from randomly filling nonesense into arbitrary
password fields such as the WireGuard private key field by setting the
`autocomplete="new-password"` attribute on any password type fields.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

modules/luci-base/htdocs/luci-static/resources/ui.js

@@ -374,6 +374,7 @@ var UITextfield = UIElement.extend(/** @lends LuCI.ui.Textfield.prototype */ {
 			'disabled': this.options.disabled ? '' : null,
 			'maxlength': this.options.maxlength,
 			'placeholder': this.options.placeholder,
+			'autocomplete': this.options.password ? 'new-password' : null,
 			'value': this.value,
 		});