Update instructions in [Configuring a subdomain] help article

[peterjuma]

What article on docs.github.com is affected?

https://docs.github.com/en/free-pro-team@latest/github/working-with-github-pages/managing-a-custom-domain-for-your-github-pages-site#configuring-a-subdomain

What part(s) of the article would you like to see updated?

Current:

To set up a www or custom subdomain, such as www.example.com or blog.example.com, you must create a CNAME file in your site's repository and configure a CNAME record with your DNS provider.

It should probably be changed to something like:

To set up a www or custom subdomain, such as www.example.com or blog.example.com, you must add your domain in the repository settings, which will create a CNAME file in your site’s repository. After that, configure a CNAME record with your DNS provider.

Additional information

Users should NOT create the CNAME file themselves, this is done automatically once they update their custom domain settings with the domain name and hence the need for this change.

If we can get the wording that would explicitly convey to users that they should NOT create the CNAME file, that will be even better

CC for visibility
@github/support-technical
@github/business-support-all

[welcome]

Thanks for opening this issue. A GitHub docs team member should be by to give feedback soon. In the meantime, please check out the contributing guidelines.

[janiceilene]

@peterjuma Thanks for opening an issue! I'll get this triaged for the right team to take a look 👀

[Yuliadocs]

Hi, can I take this issue?

[janiceilene]

You're welcome to open a PR @Yuliadocs 💖

[felicitymay]

Hi @Yuliadocs - I'm just checking through issues and found the timeline on this one really confusing. None of the various pull requests listed in the issue history above are relevant.

This issue is still available to work on.