Update ini-config.adoc, add line about lowercase letters in keywords

docs/src/config/ini-config.adoc

@@ -87,6 +87,7 @@ A variable line is made up of a variable name, an equals sign (`=`), and a value
 Everything from the first non-white space character after the `=` up to the end of the line is passed as the value,
 so you can embed spaces in string symbols if you want to or need to.
 A variable name is often called a keyword.
+A variable name that contains lowercase characters is ignored.
 
 .Variable Example
 [source,{ini}]