Add syntax files from upstream vim repository

indent/zsh.vim

@@ -0,0 +1,18 @@
+if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'vim') == -1
+  
+" Vim indent file
+" Language:             Zsh shell script
+" Maintainer:           Christian Brabandt <cb@256bit.org>
+" Previous Maintainer:  Nikolai Weibull <now@bitwi.se>
+" Latest Revision:      2015-05-29
+" License:              Vim (see :h license)
+" Repository:           https://github.com/chrisbra/vim-zsh
+
+if exists("b:did_indent")
+  finish
+endif
+
+" Same as sh indenting for now.
+runtime! indent/sh.vim
+
+endif