feat: ionic vue expose methods on vue component instance

# Bug Report

**Ionic version:**

[ ] **4.x**
[x] **5.x**

**Current behavior:**

I call IonContent scrollToTop method and console expections is thrown:
"Uncaught TypeError: content.value.scrollToTop is not a function"

**Expected behavior:**

IonContent method scrollToTop works.

**Steps to reproduce:**

1. Create ref of IonContent - ...
2. Scroll page to down
2. Call content.value.scrollToTop()

**Related code:**

```

import {IonContent} from "@ionic/vue";
import {ref} from "vue";

export default {
name: "Test",
components: {
IonContent,
},
setup(){
const content = ref();

return {
content,
scrollToTop: () => content.value.scrollToTop()
}
}
};

```

**Other information:**

**Ionic info:**

```
Ionic:

Ionic CLI : 5.4.16 (C:\Users\Damian\AppData\Local\Yarn\Data\global\node_modules\ionic)
Ionic Framework : @ionic/vue 0.5.2

Capacitor:

Capacitor CLI : 2.4.2
@capacitor/core : 2.4.2

Utility:

cordova-res : not installed
native-run : not installed

System:

NodeJS : v12.19.0 (C:\Program Files\nodejs\node.exe)
npm : 6.14.8
OS : Windows 10
```

Start by reproducing the reported Ionic Vue example with an IonContent ref and inspect the Vue component/ref integration for exposed methods. The issue is done when content.value.scrollToTop() works after the page has been scrolled.

Written by the indexing model from the issue text.