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/DateSpacing.yml

@@ -0,0 +1,7 @@
+extends: existence
+message: "It's standard to put a space before '%s'"
+ignorecase: true
+level: error
+nonword: true
+tokens:
+  - '\d{1,2}[ap]\.?m\.?'