nvim: Disable automatic formatting on save

Default the option to disable on formatting on save, but add new
key mapping to toggle it on (`<leader>sa`) and off. Still
the remaining issue of files always being 'unsaved' state when
using formatting on save, but this allows quicker toggling for
now.

nvim/.config/nvim/lua/core/mappings.lua

@@ -290,6 +290,8 @@ map(
 	{ silent = true, desc = "colorize background" }
 )
 
+map("n", "<leader>sa", "<cmd>FormatOnSave<cr>", { silent = true, desc = "toggle format on save" })
+
 -- PLUGIN: undotree
 if is_available("undotree") then
 	map("n", "<leader>su", function()

nvim/.config/nvim/lua/core/settings.lua

@@ -84,7 +84,7 @@ local globals = {
 	maplocalleader = ",",
 	tex_flavor = "latex",
 
-	format_on_save = true, -- from personal toggle function
+	format_on_save = false, -- from personal toggle function
 }
 
 for o, v in pairs(globals) do