vim: always show sign columns

I didn't like the signs over the numbers, but also don't want the
jumpiness of the 'auto' mode.

config/nvim/lua/fschauen/init.lua

@@ -90,7 +90,7 @@ local set_options = function()
   o.showbreak      = '⤷ '    -- prefix for wrapped lines
   o.scrolloff      = 3       -- min. # of lines above and below cursor
   o.sidescrolloff  = 3       -- min. # of columns to left and right of cursor
-  o.signcolumn     = 'number' -- display signs in 'number' column
+  o.signcolumn     = 'yes'   -- always display the signs column
   o.list           = false    -- don't show invisible characters initially
   o.listchars      = {
     eol = '↲',