SVG elements like linearGradient are case-sensitive and should be ignored in tagname-lowercase rule

## Describe the bug

The html element name of [ `linearGradient` ] must be in lowercase. (`tagname-lowercase`)?


## To Reproduce

```svg
...color="#ff0000"></stop></linearGradient><linearGradient id="manage_svg__a" x1="1" y1="1" x2="39" y2="...
```

## Expected behavior

SVG elements like linearGradient are case-sensitive and should use camelCase.
