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/proselint/Annotations.yml

@@ -0,0 +1,9 @@
+extends: existence
+message: "'%s' left in text."
+ignorecase: false
+level: error
+tokens:
+  - XXX
+  - FIXME
+  - TODO
+  - NOTE