Support getters and setters in the context bridge API

### Issue Details

* **Electron Version:**
* `9.x`
* **Operating System:**
* `macOS 10.15.x`

### Expected Behavior
Exposing API via `contextBridge.exposeInMainWorld` should not have side effects.

### Actual Behavior
Calling this method with an object that has a `get` property triggers it. This makes it impossible to lazy instantiate for example.

### To Reproduce
```js
contextBridge.exposeInMainWorld('vscode',{
get something(): { console.log("accessed"); }
});
```