[DOCS] Add the document of Gluten

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://www.apache.org/foundation/policies/conduct)

### Search before asking

- [X] I have searched in the [issues](https://github.com/apache/incubator-uniffle/issues?q=is%3Aissue) and found no similar issues.

### Which parts of the documentation do you think need improvement?

We don't have any gluten document. We should add them.

### Affects Version(s)

master

### Improving the documentation

The document of Gluten.

### Anything else

_No response_

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!