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/Google/Semicolons.yml

@@ -0,0 +1,8 @@
+extends: existence
+message: "Use semicolons judiciously."
+link: 'https://developers.google.com/style/semicolons'
+nonword: true
+scope: sentence
+level: suggestion
+tokens:
+  - ';'