Quote the skip list

Otherwise if people copy our example then change the skip list they can make invalid YAML

Author: peternewman

.github/workflows/codespell.yml

@@ -13,4 +13,4 @@ jobs:
         with:
           check_filenames: true
           # When using this Action in other repos, the --skip option below can be removed
-          skip: ./.git,./codespell_lib/data,./example/code.c,test_basic.py,*.pyc,README.rst
+          skip: "./.git,./codespell_lib/data,./example/code.c,test_basic.py,*.pyc,README.rst"