Add meson support

ftplugin/meson.vim

@@ -0,0 +1,19 @@
+if exists('g:polyglot_disabled') && index(g:polyglot_disabled, 'meson') != -1
+  finish
+endif
+
+" Vim filetype plugin file
+" Language:	meson
+" Original Author:	Laurent Pinchart <laurent.pinchart@ideasonboard.com>
+" Last Change:		2018 Nov 27
+
+if exists("b:did_ftplugin") | finish | endif
+let b:did_ftplugin = 1
+let s:keepcpo= &cpo
+set cpo&vim
+
+setlocal shiftwidth=2
+setlocal softtabstop=2
+
+let &cpo = s:keepcpo
+unlet s:keepcpo