Include documentation from a variable's type when you hover the variable

Issue Type: Feature request

I had hoped to see the description for the type when hovering over the value via intellisense, etc.

When I hover over context.slot I can see "The slot the disk is in." yet when I try hovering over const slot I see just the type. Is there anything to enable this? Even setting slot to Slot manually it still only shows the type.

 /** The slot the disk is in. */
type Slot = string;

interface Context {
    /** The slot the disk is in. */
    slot?: Slot
}

const func = (context: Context): Context => {
    const x = context.slot;
    const slot: Slot = context.slot;

    return {
        slot: x || slot
    };
};

func({
    slot: '1'
}).slot;

VS Code version: Code 1.43.2 (0ba0ca52957102ca3527cf479571617f0de6ed50, 2020-03-24T07:34:57.037Z)
OS version: Darwin x64 19.2.0

Start by reproducing the hover behavior with the TypeScript example in the issue and inspect the TypeScript language-service hover path used by VS Code. Determine how documentation is selected for variables whose types refer to aliases, then verify that the hover includes the type documentation without changing existing property hover behavior.