remove crossorigin from boolean attribute list

[Anthony Pothin]

<link rel="manifest" href="/app.webmanifest" crossorigin="use-credentials">

is converted by htmlnano in

<link rel="manifest" href="/app.webmanifest" crossorigin="">

Adding "collapseBooleanAttributes": false to .htmlnanorc solved my issue.

But crossorigin is not a boolean attribute.

crossorigin="use-credentials" is required for website behind credentials, even if file is in same origin.

source: https://developer.mozilla.org/en-US/docs/Web/HTML/CORS_settings_attributes#Example_Webmanifest_with_credentials

[Kirill Maltsev]

I published @fstanis fix as the version 0.2.4.