no_run and other playpen parameters not added to <code> classes if space separated

[budziq]

The additional playpen parameters (in case of inline markdown rust code) are not added to class list of generated playpen if separated by whitespace from the rust language specifier.

```rust, no_run
...

this should result in

<code class="language-rust no_run">...</code>

---

edit:
following works

```rust,no_run
...

while the space separated does not

```rust, no_run
...

edit2: This feature works somewhat outside of CommonMark spec. rust,no_run is treated as language-rust,no_run by the virtue of not containing any whitespace. CommonMark spec does not specify any mandatory behavior for the reminder of the codeblock header (which pulldown-cmark eagerly utilizes dropping everything after the whitespace)

TLNR: I learnt something new today ;)

[budziq]

The no_run,ignore,should_panic annotation is already eagerly used by several mdbooks and markdown test preprocessors. The best I can think of to make the behavior more consistent is to preprocess the markdown codeblock headers in order to get rid of whitespace. Pushing non spec conformant changes to pulldown-cmark is not realistic nor desirable.

[azerupi]

make the behavior more consistent is to preprocess the markdown codeblock headers in order to get rid of whitespace.

Sounds good to me, preprocess to remove withespace, feed to pulldown-cmark, post-process to replace commas by spaces.

[budziq]

Right. Possibly another converter could be added to utills::render_markdown along the lines of EventQuoteConverter