* Add additional root variables, rename $variable-prefix to $prefix
- Adds new root CSS variables for border-radius, border-width, border-color, and border-style
- Adds new root CSS variables for heading-color, link-colors, code color, and highlight color
- Replaces most instances of Sass variables (for border-radius, border-color, border-style, and border-width) for CSS variables inside _variables.scss
- Updates $mark-padding to be an even pixel number
- Renames $variable-prefix to $prefix throughout
* Bundlewatch
- Add CSS custom property with fallback to Sass variable
- Update docs to mention the new CSS custom property
- Rewrite some of the docs to use divider instead of separator, and add some context here and there
* Drop -x and -y as they're all the same
- Also move -width to elsewhere in the vars because it makes no sense by spacers.
- Update values of -x and -y across main Sass and docs Sass.
* Update docs to reflect changes; link to spacing utils from options page
Use new `.breadcrumb-item` class instead of child selectors and `li` tag selectors,
so as to no longer require the usage of `<ol>`-based markup.
Rename variables to follow naming conventions:
* $breadcrumb-padding-vertical => $breadcrumb-padding-y
* $breadcrumb-padding-horizontal => $breadcrumb-padding-x
Introduce new variable: $breadcrumb-item-padding
[skip sauce]
We have it set to `1` right now just to avoid compilation errors, but
it’s been replaced everywhere with our new spacer classes anywho. We’ll
likely want to remap that var to custom component vars though (e.g.,
`$pagination-margin` instead of `$spacer-y`).
