exampleSite: Add note on TOML syntax

Close #542

exampleSite/config.toml

@@ -1,5 +1,8 @@
 # Configuration of Academic
 # Documentation: https://sourcethemes.com/academic/
+#
+# This file is formatted using TOML syntax - learn more at https://learnxinyminutes.com/docs/toml/
+# Each configuration section is defined by a name in square brackets (e.g. `[outputs]`).
 
 # The URL of your website.
 # End your URL with a `/` trailing slash, e.g. `https://example.com/`.