Issue-12: Add oEmbed support

[mogmarsh]

Description

I would like to see urls for oEmbeddable content be converted into the wp:embed block

Use Case

If a url such as https://www.instagram.com/p/CSpmSvAphdf/ is found, it will be converted into

<!-- wp:embed {"url":"https://www.instagram.com/p/CSpmSvAphdf/","type":"rich","providerNameSlug":"instagram","responsive":true} -->
<figure class="wp-block-embed is-type-rich is-provider-instagram wp-block-embed-instagram"><div class="wp-block-embed__wrapper">
https://www.instagram.com/p/CSpmSvAphdf/
</div></figure>
<!-- /wp:embed -->

wp_oembed_get should be useful to see if a url is oEmbeddable.

[kevinfodness]

🍣