options: set key sequence timeout length to 420ms

Make working with `,` localleader and other key sequence commands easier
to work with by setting a longer delay

which-key menu now shows when using `,` to show localleader key mappings
availabe

Author: practicalli-johnny

options.lua

@@ -8,6 +8,7 @@ return {
     signcolumn = "auto",   -- sets vim.opt.signcolumn to auto
     wrap = true,           -- sets vim.opt.wrap
     showtabline = 0        -- sets vim.opt.showtabline
+    timeoutlen = 420,
   },
   g = {
     mapleader = " ",                 -- sets vim.g.mapleader