Enable vale for prose linting (#3)

* Enable vale in CI

* Add vale config

* Tweak vale

* Update config

* Update .gitignore

* Switch back

* Rename CI

* Add badges

* Tidy up CI

* Change image

* Configure vale

* Delint

* Update README

.github/styles/RedHat/OxfordComma.yml

@@ -0,0 +1,9 @@
+---
+extends: existence
+level: suggestion
+link: https://redhat-documentation.github.io/vale-at-red-hat/docs/main/reference-guide/oxfordcomma/
+message: "Use the Oxford comma in '%s'."
+scope: sentence
+nonword: true
+tokens:
+  - '(?:[^\s,]+,){1,} \w+ (?:and|or) \w+[.?!]'