apisix docs: add docs for `http-dubbo` plugin

Current State

Looks like it was decided in the feat PR to split out the doc task: https://github.com/apache/apisix/pull/10703#issuecomment-1910464832

That was two months ago and there doesn't seem to be any doc as of now.

Desired State

Should have some docs.

Mar 20 '24 11:03 kayx23

Is this plugin need to test using tengine? If so, there are some problems with the installation of tenginte. I have tried several methods, but none of them can be installed. I am unable to test what the final result is.

Mar 28 '24 02:03 sunheyi6

I have no idea, but it's good to share here what you have tried/worked/not worked, so that other people picking this task up can reference.

Mar 28 '24 09:03 kayx23

Hi @ShenFeng312 are you available some time to add some doc for http-dubbo plugin?

Apr 28 '24 09:04 kayx23

@kayx23 Sorry for the delay. I'll add the documentation as soon as possible.

Apr 29 '24 05:04 ShenFeng312

Is this plugin need to test using tengine? If so, there are some problems with the installation of tenginte. I have tried several methods, but none of them can be installed. I am unable to test what the final result is.

This plugin does not require Tengine.

Apr 29 '24 05:04 ShenFeng312