Add a default value for components directory option

[zachleat]

I think components: "_components/**/*.webc" is probably appropriate.

Will need to handle ignores and watch targets correctly!

Suggested by @cfjedimaster here: https://www.raymondcamden.com/2022/10/16/first-experience-building-with-eleventys-webc-plugin

[zachleat]

I would also note that the reason we didn’t just use components: "_includes/**/*.webc is to avoid conflicts between WebC Components and WebC for Eleventy Layouts. We don’t want to waste resources compiling a WebC Layout file as a component (and vice versa).

[zachleat]

The other thing I would note here is that both _includes and _layouts are relative to the input directory, but components is not 😔

https://www.11ty.dev/docs/config/#directory-for-includes
https://www.11ty.dev/docs/config/#directory-for-layouts-(optional)

https://www.11ty.dev/docs/languages/webc/#global-no-import-components

One future-compatible idea here is to add an alias here to make the path relative to the input directory (we already have one for the root directory for webc.components in front matter).

(Aliasing docs: https://www.11ty.dev/docs/languages/webc/#webcimport https://www.11ty.dev/docs/languages/webc/#declaring-components-in-front-matter)

[zachleat]

This will ship with _components/**/*.webc in Eleventy WebC v0.7.0!