Press This: do quote user selection when dealing with an oembed provider's site.

[stephdau]

We recently (#31637) made the decision to not blockquote text underneath embeds, when the source site is recognized as an oembed provider (Youtube, SoundCloud, etc).

This works when we discover a page's description (Open Graph tags, etc), but we should probably quote the text if the user went to the extent of actually selecting some in the source page (s in $_POST or $_GET).

The attached patch does this. We should also discuss if when we do so, we should also include the standard attribution link, as we do for other cases. I'd argue it's not necessary, since the embeds all have direct links to the source, but I'm opened to it.

I'm listing this as a bug because we didn't discuss it at the time, but it came up as an expectation when ​brought up.

[ryan]

User selection is deliberate enough that including it beneath the embed seems reasonable. Omitting attribution from the quote when there is an attributed embed sounds fine.

[azaozz]

In 31894:

Press This: on sites that support oEmbed, if the user has selected some text, quote it below the embed.
Props stephdau. Fixes #31763.

[stephdau]

Thanks Oz.