[Doc] Add a proper way to submit website issues and improvement proposals

### Search before asking

- [X] I searched in the [issues](https://github.com/apache/pulsar/issues) and found nothing similar.

### What issue do you find in Pulsar docs?

The GitHub issue templates lack a way to submit website issues and improvement proposals for the website

### What is your suggestion?

Just make this sensible. :) There needs to be at least labeling for website related issues.
The "doc-required" label is also nonsense to me for document issues.

### Any reference?

_No response_

### Are you willing to submit a PR?

- [ ] I'm willing to submit a PR!