vifm: Add toggle icon mapping 'ti'

Added mapping to toggle classify prefix icons on or off quickly
using my semi-established 'toggle' submenu with the mapping
`ti` (for toggle icon).

terminal/.config/vifm/vifmrc

@@ -172,6 +172,13 @@ command! fzfcd : set noquickview
                 \| if $FZF_PICK != ''
                 \|     execute 'cd' fnameescape($FZF_PICK)
                 \| endif
+" show or hide the devicon prefix for files
+command! toggleicons :
+                \| if &classify == ''
+                \|     source $VIFM/favicons.vifm
+                \| else
+                \|     set classify=''
+                \| endif
 " }}}
 " vifminfo {{{
 " ------------------------------------------------------------------------------
@@ -269,10 +276,7 @@ nnoremap tN :windo toggle number<cr>
 nnoremap tR :windo toggle relativenumber<cr>
 nnoremap te :execute ':tree! | echo ":tree"'<cr>
 nnoremap tt t
-
-" zo shows hidden files, mimicking fold open in vim -- why does zc not close
-" again?
-nnoremap zc zm
+nnoremap ti :toggleicons<cr>
 
 " external commands
 " extract currently selected file(s)