Support single element or top level arrays

Building on @theianjones's proposal in #3.

> 1 open question is how to represent an array with a single element. The only idea I had was fragments like `<>...`. But that would be a separate PR anyway.

Given a component-like function:

```jsx
const Aliases = () => (
<>



)
```

Expect ``:

```json5
[
{
// name: "alias",?
from: "react",
to: "preact-compat",
},
{
// name: "alias",?
from: "react-dom",
to: "preact-compat",
},
]
```

Given:

```jsx
const Resolve = () => (

<>



)
```

Expect ``:

```json5
{
name: "resolve",
alias: [
{
from: "react-dom",
to: "preact-compat",
},
],
}
```

從 issue #3 中引用的提案開始，然後追蹤 JSX 範例目前是如何轉換為 JSON 的。驗證所述的兩種情況：返回多個頂層元素的元件會變成陣列，而巢狀在 parent 中的單一元素會變成包含一個元素的陣列。Issue 指出，fragment 語法是另一個獨立問題。

由索引模型根據 Issue 內容生成。