Add example for naming style adapter

examples/naming_style.rb

@@ -0,0 +1,19 @@
+require 'bundler/setup'
+require 'flipper'
+require 'flipper/adapters/naming_style'
+
+Flipper.configure do |config|
+  config.use Flipper::Adapters::NamingStyle, :snake # or :camel, :kebab, :screaming_snake, or a Regexp
+end
+
+# This will work because the feature key is in snake_case.
+Flipper.enable(:snake_case)
+
+begin
+  # This will raise an error because the feature key is in CamelCase.
+  Flipper.enable(:CamelCase)
+rescue Flipper::Adapters::NamingStyle::InvalidFormat => e
+  puts "#{e.class}: #{e.message}"
+else
+  fail "An error should have been raised, but wasn't."
+end