support a directory of definitions when configuring the plugin

[thescientist13]

Currently, to tracking custom element definitions in the WCC plugin, you have to provide them individually, e.g.

eleventyConfig.addPlugin(wccPlugin, {
  definitions: [
    new URL('./path/to/my-component.js', import.meta.url),
    new URL('./path/to/my-other-component.js', import.meta.url)
  ]
});

It would be nice if this plugin could detect that a directory is provided, and just glob all the files within that, e.g.

eleventyConfig.addPlugin(wccPlugin, {
  definitions: [
    new URL('./path/to/my/components', import.meta.url),
  ]
});

Will need to make sure this is compatible with cache busting / live reloading in the plugin.

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Couple questions / thoughts

1. Should we just filter on .js / .ts files, or include CSS files too? (probably yes?)