Update pkg/ffapi/openapi3.go

Co-authored-by: Enrique Lacal <enrique.lacal@kaleido.io>
Signed-off-by: Chris Bygrave <chris.bygrave@kaleido.io>

Author: chrisbygrave

pkg/ffapi/openapi3.go

@@ -76,6 +76,7 @@ type BaseURLVariable struct {
 
 var (
 	customRegexRemoval = regexp.MustCompile(`{(\w+)\:[^}]+}`)
+    // Check ffExtension key starts with "x-"
 	ffExtensionKeyRegexp = regexp.MustCompile(`^x-.+$`)
 )