parse-options: add link to doc file in parse-options.h

Add a link to Documentation/technical/api-parse-options.txt in parse-options.h
So the developers would know where to find more info about the API.

Signed-off-by: Heba Waly <heba.waly@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: HebaWaly

parse-options.h

@@ -1,6 +1,10 @@
 #ifndef PARSE_OPTIONS_H
 #define PARSE_OPTIONS_H
 
+/**
+ * Refer to Documentation/technical/api-parse-options.txt for the API doc.
+ */
+
 enum parse_opt_type {
 	/* special types */
 	OPTION_END,