Consider re-intepreting youtube image links as embedding videos

Following markdown image links could be used to link to a youtube video using a thumbnail.
Perhaps we should investigate if we can directly embed these.

There is perhaps some concerns around performance, and whether it would be annoying with videos embedded in markdown.

Note: This is not a fully designed feature yet, just an idea.

------------------------------

```
[](http://www.youtube.com/watch?v=)
```

```
[](http://www.youtube.com/watch?v=)
```

```
[](http://www.youtube.com/watch?v=)
```

The issue provides only example Markdown links and does not identify files, tests, or an implementation entry point. First locate the Markdown rendering path and assess YouTube detection, performance, and user experience; the work is done only after the embedding behavior and its scope are designed and agreed.

Written by the indexing model from the issue text.