Not clear how to describe multiple licenses

Hi,

The [documentation for the license attribute](https://docs.conan.io/1/reference/conanfile/attributes.html#license) states that

> This attribute can contain several, comma separated licenses. It is a text string, so it can contain any text, including hyperlinks to license files elsewhere.

However, it's not clear whether multiple licenses should be a single string containing comma-separated licenses like so:

```
license = "MIT, GPL-3.0-or-later"
```

or a tuple of comma-separated strings:

```
license = "MIT", "GPL-3.0-or-later"
```

I've been able to find one example and one comment from @ericriff where it's a tuple:

https://github.com/conan-io/conan-center-index/blob/bab95647f8588594a809d59af368ffd798f602da/recipes/restbed/all/conanfile.py#L20

https://github.com/conan-io/conan-center-index/issues/4333#issuecomment-765448974

Is this correct?

Regardless, could the documentation be updated to clarify which is the case? Or should it be both?

Thanks,

Bob Ham

Start with the linked documentation for the license attribute and inspect the existing wording and examples. Confirm with the project whether multiple licenses use one comma-separated string, a tuple, or both; done means the documentation explicitly states the supported syntax and includes an unambiguous example.

Written by the indexing model from the issue text.