Guide: add description of web app at ports.macports.org

[JDLH (Jim DeLaHunt)]

I do not see any mention of the webapp running at ​https://ports.macports.org in the ​MacPorts Guide. I think the information on recent builds of ports presented by this web app is quite helpful to a port maintainer. Thus this tool should be mentioned in the Guide, with a brief summary of what it does, and a link to the ​tool's own documentation.

I would suggest adding this mention to ​section 4.8. **MacPorts' buildbot**.

[JDLH (Jim DeLaHunt)]

Pull request ​https://github.com/macports/macports-guide/pull/45 addresses this ticket.

[Jim DeLaHunt <from+project_by_git@…>]

In 9a1d2f2256206ce8d97d04de52fcfda34ec3061d/macports-guide (master):

Add info on ​https://ports.macports.org to buildbot section, ​https://github.com/macports/macports-guide/pull/63001

Guide section 4.8. "MacPorts' buildbot" did not mention the web page
at ​https://ports.macports.org/ at all. Add a one-paragraph summary of
what this page can do for port developers to the end of the section.

Also, the previous part of the section mentioned the "waterfall" and
"builders" pages on the ​https://build.macports.org web page, but did not
mention the URL itself. So I added that URL. Also resequence the
sentences to soften the claim that these views are "most useful", since
I don't think these views are as good as the ports.macports.org page.

This addresses Trac ticket ​https://github.com/macports/macports-guide/pull/63001, "Guide: add description of web app
at ports.macports.org", #63001 .