Add documentation, incubator check

Author: froggleston

_extras/customization.md

@@ -35,6 +35,25 @@ configure some site-wide variables and make the site function correctly:
   it will appear in the "jumbotron" (the gray box at the top of the page). This variable is also
   used for the title of the extra pages. The README contains [more information about extra pages](https://github.com/carpentries/workshop-template#creating-extra-pages).
 
+### Slug Validation
+
+For workshops teaching a core or mix and match curriculum, i.e. 
+where `carpentry` is set to `swc`, `dc`, or `lc`, the website build
+will check that your repository name matches the Carpentries slug 
+format - `YYYY-MM-DD-site[-online]`, e.g. `2024-05-07-oomza-online`.
+
+**If your repository name does not match this format, the build will 
+fail, and will direct you to rename your workshop website repository 
+to a valid slug.** You will then need to commit a change to the repo 
+to rebuild the site, e.g. adding a space or other inconsequential 
+change to the `README.md`.
+
+Workshop websites using `cp` or `incubator` will go through the same
+check, but the build will not fail if the repo name does not match 
+the slug format. You will see a warning in the build output instead.
+
+### Incubator lessons
+
 For workshops teaching lessons in The Carpentries Incubator,
 i.e. where `carpentry` is set to `incubator`,
 you should uncomment the following three fields in

bin/workshop_check.py

@@ -420,7 +420,7 @@ def check_slug(reporter, filename, repo_dir):
                 print(fail_msg.format(repo_name, slugfmt))
                 sys.exit(1)
 
-        elif carpentry in ('cp'):
+        elif carpentry in ('cp', 'incubator'):
             warn_msg = (
                 'Website repository name `{0}` does not match the suggested slug format: `{1}`. '
                 'If teaching a workshop which you are collecting surveys for or are submitting into AMY, '