Support for "Derived Class" type of functionality for interfaces

**DocFX Version Used**: 2.32

**Template used**: `default`

**Steps to Reproduce**:

1. Have code with interface and a class that implements that interface
2. Generate metadata, build the docs
3. Look at the generated interface API reference page

**Expected Behavior**:
See a list of implementations of current interface that I am browsing.

**Actual Behavior**:
Interface has no idea what implements it.

Now, I know that only classes support `DerivedClasses` property (`derivedClasses` in view model). It's documented, and it's obvious from the [source code](https://github.com/dotnet/docfx/blob/e8019fe187dc9e314c3e10e92ea2380abe0336ed/src/Microsoft.DocAsCode.Metadata.ManagedReference/Resolvers/SetDerivedClass.cs#L58).

However seeing classes that implement an interface, when reading the interface's API ref page would be super useful. And in my humble opinion it doesn't seem to be too different from derived classes, doesnt seem to be too hard to implement. Could be wrong...

Personally I have a bunch of use cases for such functionality. Mostly related to marker interfaces, and I have no easy way to have a single page with all possible implementations in API Reference docs.