add tag files to .gitignore

The auto-generated makefile targets CTAGS, GTAGS and TAGS generate files
locally that should not be checked-in into the source code. This change
adds these files to the .gitignore file. The list of files match those
in distclean-tags target.

.gitignore

@@ -33,3 +33,15 @@
 
 Makefile
 Makefile.in
+
+GPATH
+GRTAGS
+GSYMS
+GTAGS
+ID
+TAGS
+cscope.files
+cscope.in.out
+cscope.out
+cscope.po.out
+tags

AUTHORS

@@ -82,6 +82,7 @@ Gergely Risko <gergely@risko.hu>
 Sung Pae "guns" <self@sungpae.com>
 Helmut Grohne <helmut@subdivi.de>
 Hugo Haas <hugo@larve.net>
+Husain Alshehhi <husain@alshehhi.io>
 Jaroslav Suchanek <jaroslav.suchanek@gmail.com>
 Jeremie Courreges-Anglas <jca@openbsd.org>
 Klemens Nanni <kn@openbsd.org>