macro arguments with comma not properly supported

Nobody has claimed this yet.

I have created a macro to quickly make quotations which should like this:

If I put the quote argument in quotation marks it looks like this (the quotation marks are shown):
```
{{quote "All models are wrong, but some are useful", George Box}}
```

But if I remove them, then it (of course) can't tell where the quote ends:
```
{{quote All models are wrong, but some are useful, George Box}}
```

It would be nice if the quotation marks could be removed. Is there a canonical way to do this?

Start by locating mldoc's macro argument parsing and reproduce the reported {{quote ...}} examples, especially the comma-containing quotation. The work is done when a quote containing commas can be passed without visible quotation marks while the author argument remains separate and existing macro behavior is preserved.

Written by the indexing model from the issue text.