A Vue Directive to call a callback when a click occurs *outside* of the element
the directive is bound to. Any clicks on the element or any descendant elements are ignored.

## Usage

```html
<script>
import { GlOutsideDirective as Outside } from '@gitlab/ui';

export default {
  directives: { Outside },
  methods: {
    onClick(event) {
      console.log('User clicked somewhere outside of this component', event);
    },
  },
};
</script>

<template>
  <div v-outside="onClick">Click anywhere but here</div>
</template>
```

## Caveats

- If a click event is stopped (e.g., via `event.stopPropagation()`) before it
  bubbles up to the `document`, it cannot be detected by `GlOutsideDirective`.
- Clicks cannot be detected across document boundaries (e.g., across an
  `iframe` boundary), in either direction.