Documentation does not explain what generics represent

#### Documentation Feedback

In docs it would be helpful to have documentaion for declared TS generics.
For example, I open `MatDatepickerInputEvent` [docs](https://material.angular.io/components/datepicker/api#MatDatepickerInputEvent) and see `S` and `D` generics.
And from the docs it's unclear what these `S` and `D` represent!

I think it should be documented similar to as Java does it.
For example, a [docs](https://docs.oracle.com/en/java/javase/15/docs/api/java.base/java/util/function/Function.html) of Java's standard type `Function` contain a section

> Type Parameters:
> T - the type of the input to the function
> R - the type of the result of the function

Start with the MatDatepickerInputEvent entry in the Angular Material datepicker API documentation and inspect how its TypeScript declaration is presented. Document what the S and D type parameters represent, following the type-parameter style shown in the linked Java documentation. Done means newcomers can understand both generics from the API docs.

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