Support custom property --scroll-behavior

[jonaskuske]

Support usage of a CSS custom property --scroll-behavior

While the current workaround using font-family is the only reliable way of putting custom information into CSS that works across all browsers, every modern browser supports custom properties.

To make this package more approachable (and not immediately confront users with a reliable but sketchy-looking CSS hack), the custom property --scroll-behavior should be both supported and recommended as the default way to set scroll behavior.

The font-family workaround (and inline styles) will continue to be supported, but it should be clearly communicated that this is only to support legacy browsers like Internet Explorer – for users that are only looking to bring smooth scrolling to modern browsers like Edge and Safari, --scroll-behavior is enough.

postcss-smoothscroll-anchor-polyfill needs to be updated in accordance with this, transpiling scroll-behavior to --scroll-behavior and only creating the font-family workaround if the users browserslist includes support for legacy browsers.

[jonaskuske]

Fixed with v.1.3.0