Add additional systemd files, based on systemd.syntax(7)

Author: cbcoutinho

ftdetect/systemd.vim

@@ -7,3 +7,9 @@ au BufNewFile,BufRead *.swap      set filetype=systemd
 au BufNewFile,BufRead *.target    set filetype=systemd
 au BufNewFile,BufRead *.timer     set filetype=systemd
 au BufNewFile,BufRead *.slice     set filetype=systemd
+au BufNewFile,BufRead *.scope     set filetype=systemd
+au BufNewFile,BufRead *.nspawn    set filetype=systemd
+au BufNewFile,BufRead *.unit      set filetype=systemd
+au BufNewFile,BufRead *.link      set filetype=systemd
+au BufNewFile,BufRead *.netdev    set filetype=systemd
+au BufNewFile,BufRead *.network   set filetype=systemd