ci(docs): Fail when build aborts from broken links (#2266)

Using `set -ex` will exit the script as soon as a non-zero exit code is returned, such as when the docker image fails building the docs due to `build --strict` catching broken links. This also removes the need for `|| exit` when changing directory.

This seems fine for a small script, but AFAIK an alternative fix is just adding `|| exit` to the end of the `docker run` command too? There appears to be advice [against adopting `-e` carelessly](http://mywiki.wooledge.org/BashFAQ/105), while others [encourage `-e`](http://redsymbol.net/articles/unofficial-bash-strict-mode/). I know that several maintainers here have preference towards `set -e` so I've kept the original PR solution.

Additionally:

- `-x` is used to improve command visibility when reviewing the workflow log output.
- `--name` isn't necessary, but was part of the original PR.
- I've chosen not to include `-o pipefail`, only because no pipes are used in this script.

* docs(fix): Fix broken links

* ci(docs): Added inline docs

Extra documentation context for maintainers to quickly grok what's going on.

* chore(docs): Minor typo fix by wernerfred

Added from their related PR by request.

.github/workflows/scripts/docs/build-docs.sh

@@ -1,15 +1,20 @@
 #!/bin/bash
+set -ex
 
+# PWD should be at the project docs/ folder.
 # `--user` is required for build output file ownership to match the CI user,
 #  instead of the internal root user of the container.
+# `build --strict` ensures the build fails when any warnings are omitted.
 docker run \
   --rm \
   --user "$(id -u):$(id -g)" \
-  -v "${PWD}:/docs" \
+  --volume "${PWD}:/docs" \
+  --name "build-docs" \
   squidfunk/mkdocs-material:7.3.5 build --strict
 
 # Remove unnecessary build artifacts: https://github.com/squidfunk/mkdocs-material/issues/2519
-cd site || exit
+# site/ is the build output folder.
+cd site
 find . -type f -name '*.min.js.map' -delete -o -name '*.min.css.map' -delete
 rm sitemap.xml.gz
 rm assets/images/favicon.png