add file docs/guides/index.cn.md,translation into Chineses

[jimcat8]

add new file

[sspencerwire]

@jimcat8 I was looking at your document and said, "wait, that shouldn't be there and then saw that it IS there in the English language landing page! This is an error that you have found, and I'll fix it in the English version. I will need you to push a fix to your PR to correct this there as well. The error in the English version is:

If you want to find out how to help in the ongoing development of Rocky Linux, click on the Rocky Specific section,

That section was there for a time and then removed. The landing page did not get updated. Thanks for finding this error!!!
Steve

[sspencerwire]

If you just remove this much of this one line in your PR:

click on the Rocky Specific section, which includes a section on development, and

Which leaves this remaining:

join the Mattermost Development channel

[sspencerwire]

Thanks for your willingness to edit this @jimcat8 ... I'm merging now. Thanks, Steve