Update README to include Liquid conditionals note

Added a note about the external.yml file supporting Liquid conditionals.

Author: qamro

data/glossaries/README.md

@@ -1,5 +1,6 @@
 # Glossaries
 
+
 * `external.yml` contains customer-facing glossary entries.
   * Strings within `external.yml` support Liquid conditionals. See [contributing/liquid-helpers.md](/contributing/liquid-helpers.md).
 * `candidates.yml` contains terms that should potentially be in the external glossary but haven't been defined yet.