Docs: Contact plugin/theme maintainers for those issues

CONTRIBUTING.rst

@@ -26,16 +26,21 @@ Before you ask for help, please make sure you do the following:
 * latest releases of libraries used by Pelican
 * no plugins or only those related to the issue
 
-**NOTE:** The most common sources of problems are anomalies in (1) themes,
-(2) settings files, and (3) ``make``/``invoke`` automation wrappers. If you can't
-reproduce your problem when using the following steps to generate your site,
-then the problem is almost certainly with your chosen theme and/or settings
-file (and not Pelican itself)::
+**NOTE:** The most common sources of problems are anomalies in (1) themes, (2)
+plugins, (3) settings files, and (4) ``make``/``invoke`` automation wrappers.
+If you can't reproduce your problem when using the following steps to generate
+your site, then the problem is almost certainly with one of the above-listed
+elements (and not Pelican itself)::
 
     cd ~/projects/your-site
     git clone https://github.com/getpelican/pelican ~/projects/pelican
     pelican content -s ~/projects/pelican/samples/pelican.conf.py -t ~/projects/pelican/pelican/themes/notmyidea
 
+If you can generate your site without problems using the steps above, then your
+problem is unlikely to be caused by Pelican itself, and therefore please
+consider reaching out to the maintainers of the plugins/theme you are using
+instead of raising the topic with the Pelican core community.
+
 If despite the above efforts you still cannot resolve your problem, be sure to
 include in your inquiry the following information, preferably in the form of
 links to content uploaded to a `paste service`_, GitHub repository, or other