ignoreDeclaration does not ignore lower case doctype declaration

* [x] Are you running the latest version?
* [x] Have you included sample input, output, error, and expected output? 
* [x] Have you checked if you are using correct configuration?
* [x] Did you try online [tool](https://naturalintelligence.github.io/fast-xml-parser/)?
* [x] Have you checked the [docs](https://github.com/NaturalIntelligence/fast-xml-parser/tree/master/docs) for helpful APIs and examples?

### Description
`ignoreDeclaration` does not ignore lower case doctype declaration.
### Input


### Code
```js
const html = `<!doctype html><html></html>`;

const parser = new XMLParser({
  ignoreDeclaration: true,
});
let jObj = parser.parse(html);

console.log(jObj);
```

### Output
```js
{ '!doctype': { html: '' } }
```

### expected data
```js
{ html: '' }
```

**Would you like to work on this issue?**

- [ ] Yes
- [x] No

[Bookmark](https://github.com/NaturalIntelligence/fast-xml-parser/stargazers) this repository for further updates. Visit [SoloThought](https://solothought.com) to know about recent features.

Navigation Menu

Uh oh!

Uh oh!

ignoreDeclaration does not ignore lower case doctype declaration #870

Description

Input

Code

Output

expected data

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Uh oh!

Uh oh!

ignoreDeclaration does not ignore lower case doctype declaration #870

Description

Description

Input

Code

Output

expected data

Activity

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions