Support for cref in inheritdoc tags

[matkoch]

Following up on #247.

In regards to this comment, I would like to refer to my comment in the related roslyn issue again.

[Still34]

Would this ever be supported? I'd like to see it in v3 if possible.

[rymeskar]

+1, to be more precise.

In fact, I would appreciate an introduction of all the currently non-supported features from the list.

[amirebrahimi]

Any feedback before I create a PR? Here's my proposed solution:
1ae5ba1