JSX elements with no children don't self close on format

**Describe the bug**

JSX elements with no children don't self close on format.

Deno version: 1.37.0

**Input Code**

```tsx
const a = <div></div>
```

**Expected Output**

```tsx
const a = <div />
```

**Actual Output**

```tsx
const a = <div></div>
```
