Add a lint check to prevent whitespace issues

Whitespace issues as understood by git (by default) are trailing
whitespace at EOL, whitespace on an otherwise empty line, a space
character immediately followed by a tab character in the indentation of
a line, and multiple newlines at EOF.

References:
- https://git-scm.com/docs/git-diff#Documentation/git-diff.txt---check
- https://peter.eisentraut.org/blog/2014/11/04/checking-whitespace-with-git

.github/workflows/lint.yml

@@ -36,3 +36,11 @@ jobs:
         files_with_crlf="$(git ls-files --eol | awk '$1 ~ "crlf"')"
         echo "$files_with_crlf"
         [ "$files_with_crlf" == "" ] || exit 1
+
+  no-whitespace-issues-in-git:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+    - uses: actions/checkout@v4
+    - name: Check for whitespace issues in the repository
+      run: git diff --check $(git hash-object -t tree /dev/null) HEAD