Anchor Positioning API

[vibdev]

Some part of the CK styling system isn't going to be compatible with the incoming anchor positioning api.

Namely the helpers seem to automatically detect strings that start with -- and wrap them in a var()

Creating an anchor is straightforward. Apply the anchor-name property to the selected element, and assign it a unique identifier. This unique identifier must be prepended with a double dash, much like a CSS variable.

e.g.

 .anchor-button {
     anchor-name: --anchor-el;
 }

Bug Repro:
https://stackblitz.com/edit/canvas-kit-react-v12-starter-w7cqqu-fbcpu4wq?file=src%2FApp.tsx

the crux is

const anchorVars = createVars('anchor');
const anchorDefaults = anchorVars({ anchor: '--anchor-el' });

is equivalent to 
const anchorVars = createVars('anchor');
const anchorDefaults = anchorVars({ anchor: 'var(--anchor-el)' });

but in this case I don't want the var parts because --anchor-el is not a custom property