Detail docs for embed_html, embed_content and embed_content_meta

[matthieuscarset]

I was trying to find the right action to customize the output of embed post and I found hard to understand which action I should use and how to use it in my plugin between.

I first found that doc:
​https://developer.wordpress.org/reference/hooks/embed_html/

Possible improvement

1. Give details about what this filter actually filters (only the <iframe> tag)

2. Add links to the others related actions:

​https://developer.wordpress.org/reference/hooks/embed_content
​https://developer.wordpress.org/reference/hooks/embed_content_meta/

3. Add example of how to use each one of these filters

Feel free to ask me further details if needed.
Thanks!
Matt

[musus]

Change description of $output for clarification.

[DrewAPicture]

In 40945:

Docs: Add a clarification to the description about what the $output parameter in the embed_html filter doc represents.

Props musus.
Fixes #37752.