feat: extended FAB

# Feature Request

**Ionic version:**
[x] **5.2.1**

**Describe the Feature Request**
Ion Fab Expanded button: As per google material design, there is an option to add an expanded version of ion-fab. Check this link to see more [https://material.io/components/buttons-floating-action-button#extended-fab](https://material.io/components/buttons-floating-action-button#extended-fab)

**Describe Preferred Solution**
Currently there is no option in the framework for us to use the expanded version. It might be activated using a directive:
```

Compose

```
**Additional Context**
Gmail App:
[Screenshot](https://cdn.vox-cdn.com/thumbor/PzhykRfqcf_gRZnLtKrzLHxi9-I=/0x1498:1080x2160/1200x800/filters:focal(756x1929:928x2101)/cdn.vox-cdn.com/uploads/chorus_image/image/66898321/Screenshot_20200605_092605.0.png)

该请求针对 ion-fab-button 组件，并提出一种带有图标和 Compose 标签的扩展用法。首先定位该组件及其现有测试；当扩展 FAB 与链接的 Material Design 示例保持一致地得到支持，并且所提议的标记已由测试覆盖时，即视为完成。

由索引模型根据 Issue 内容生成。