use markdown friendly-snippets in pandoc documents

lua/autocommands.lua

@@ -6,6 +6,7 @@ vim.api.nvim_create_autocmd({"BufEnter", "BufWinEnter"}, {
   group = markdown,
   callback =  function()
     vim.o.filetype = 'pandoc'
+    require('luasnip').filetype_extend("pandoc", {"markdown"})
     vim.o.spell = true
     vim.o.spelllang = 'en'
     vim.o.formatoptions = "qj"