Button focus() enhancements

[ryanbmarx]

Currently, Button.svelte does not forward focus events. Adding on:focus to the element would solve this.

Also, to programmatically assign focus, access to the HTML element is required, but currently the Button component does not allow access. Perhaps this would work:

export let el: HTMLElement;

<button bind:this={el}

Which would allow buttonInstance.el.focus() in parent components.

I'm happy to generate a PR if these approaches are acceptable.

[metonym]

Note that the Button does support programmatic focus via the ref prop:

<script>
  import { Button } from "carbon-components-svelte";

  let ref;

  $: ref?.focus();
</script>

<Button bind:ref>Primary button</Button>

However, I do think that forwarding focus to button events is reasonable. A PR would be welcome.

[metonym]

Fixed in v0.82.8