Fix cropped handle icon

Problem/Motivation

When using common CSS normalization stylesheets, the handle icon is cropped almost completely out of view.

Steps to reproduce

This is reproducible when a theme specifies something like one of the following:

*,
::before,
::after {
  box-sizing: border-box;
}

*,
::before,
::after {
  box-sizing: inherit;
}

See https://github.com/csstools/sanitize.css/blob/092d0d85922bfa72d28e9e8d25...
See https://github.com/sindresorhus/modern-normalize/blob/5d8b1e5c8a167948e9...
See https://github.com/uswds/uswds/blob/42907b9ef1a8dfa859730e91d03482f2283b...

Use a theme that implements one of the many commonly used normalization stylesheets: sanitize.css, modern-normalize.css, etc.

Proposed resolution

Ensure .handle styling is in place that works with and without these box-sizing normalizations.