First attempt at testing for descriptors

Attempt to start testing for a few items we use to describe
elements on a page, and recommend the correct words or phrases
instead. I changed the format of the returned message to give us more
flexibility in describing how to rewrite the sentence. Not all of
them are straightforward swaps.

doc/.vale/gitlab/ElementDescriptors.yml

+---
+# Suggestion: gitlab.ElementDescriptors
+#
+# Suggests the correct way to describe elements in a form.
+#
+# For a list of all options, see https://errata-ai.github.io/vale/styles/
+extends: substitution
+message: 'When describing elements, %s "%s".'
+link: https://docs.gitlab.com/ee/development/documentation/styleguide/index.html#language
+level: suggestion
+ignorecase: true
+swap:
+  button: 'if possible, rewrite to not use'
+  area: 'use "section" instead of'