patch 9.0.2128: runtime(swig): add syntax and filetype plugins

Add syntax and filetype plugins for SWIG (Simplified Wrapper Interface
Generator) description files.

The default syntax for .i files highlights comments in a reverse
color scheme which doesn't look well.  This syntax builds
on vim's c++ syntax by adding highlighting for common swig
directives and user defined directives.  For an alternative
syntax, see vimscript #1247 (which I found after writing this).

closes: #13562

Co-authored-by: Matěj Cepl <mcepl@cepl.eu>
Co-authored-by: Julien Marrec <julien.marrec@gmail.com>
Signed-off-by: Julien Marrec <julien.marrec@gmail.com>
Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
index d99c8c7..977bb5d 100644
--- a/.github/CODEOWNERS
+++ b/.github/CODEOWNERS
@@ -224,6 +224,7 @@
 runtime/ftplugin/ssa.vim		@ObserverOfTime
 runtime/ftplugin/swayconfig.vim		@jamespeapen
 runtime/ftplugin/systemverilog.vim	@Kocha
+runtime/ftplugin/swig.vim		@jmarrec
 runtime/ftplugin/tap.vim		@petdance
 runtime/ftplugin/tcsh.vim		@dkearns
 runtime/ftplugin/tidy.vim		@dkearns
@@ -502,6 +503,7 @@
 runtime/syntax/sudoers.vim		@e-kwsm
 runtime/syntax/svn.vim			@hdima
 runtime/syntax/swayconfig.vim		@jamespeapen
+runtime/syntax/swig.vim			@jmarrec
 runtime/syntax/systemverilog.vim	@Kocha
 runtime/syntax/tags.vim			@cecamp
 runtime/syntax/tap.vim			@petdance