Detect if the current URL has a WebDAV share #129
Description
Currently if I'm on a page that doesn't have a WebDAV share and executing the bookmarklet then it's executed but as result I have a broken page.
It's fine, but maybe we can change order and first check OPTIONS and only then render the UI. And if the URL doesn't have a DAV header then gracefully say it to a user.
I'm going to implement this for the browser extension #128 but this may be done by the webdav-js itself.