Add grammar linting tests for Latin phrases

The GitLab style guide encourages simple, clear language, and
specifically suggests not using Latin terms such as "e.g." and
"i.e." because sentences are generally clearer if they're
rewritten to not need these phrases. This rule tests for variants
of a few common Latin phrases.

doc/.linting/vale/styles/gitlab/LatinTerms.yml

+---
+# `extends` indicates the Vale extension point being used.
+# Full list of styles: https://errata-ai.github.io/vale/styles/
+extends: substitution
+
+# Substitution rules can display the matched and suggested strings in the 
+# message shown to the user. The first use of %s prints the suggested option,
+# and the second use of %s displays what was found in the text.
+message: Use "%s" instead of "%s," but consider rewriting the sentence.
+
+# Should a result be flagged as a suggestion, warning, or error?
+# Results that fall below the MinAlertLevel set in 
+# https://gitlab.com/gitlab-org/gitlab/blob/master/.vale.ini won't be shown.
+level: warning
+
+# Should a match be case-insensitive or case-sensitive?
+# Acceptable values are 'true' or 'false'
+ignorecase: true
+
+# Should this rule be limited to a specific scope? If yes, uncomment the line.
+# Possible scopes: https://errata-ai.github.io/vale/formats/#available-scopes
+# scope: heading
+
+# Should this rule ignore normal word boundaries, such as \b ?
+# Acceptable values are 'true' or 'false'
+nonword: true
+
+# What is the source for this rule?
+link: https://docs.gitlab.com/ee/development/documentation/styleguide.html#language
+
+# The 'swap' section provides a list of values, one per line, in the form of
+# $bad: $good
+swap:
+  e\.g\.: for example
+  e\. g\.: for example
+  i\.e\.: that is
+  i\. e\.: that is
+  etc\.: and so on
+  et cetera: and so on